Peggy, I have your book and it has been very helpful. However, I am now totally frustrated. I have a 1996 37.5 Legand Hunter with a factory installed Jabsco toilet. This past winter I replaced the old black hose with new white hose, I had a new pump put in, I backwashed the air vent and I'm still having a problem. Everything seems to be working okay but I keep getting a back flow into the toilet bowl after the boat sits idle for a week or two. I ask the guy that installed the new pump if he replaced the joker valve and he said he did. I'm not sure if you are familar with the set up on my particular boat but the bottom of the holding tank is actual higher than the toilet. This means that if you don't get everything flushed to the tank it will come back to the toilet. If the joker valve is doing it's job the waste should not get back into the toilet. Therefore I have to believe there is a problem with the joker valve. I'm ready to yank the damn Jabsco out and install a new toilet if I have to so any ideas would be appreciated. I'm tired of everything in the boat swelling. Tom S/V At Last
Tired of the swelly boat
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I don't think a new toilet will solve your problem
Most boat owners don't know how to use the dry mode...they flush only in the wet mode except to move the last of the water out of the bowl...not realizing that any manual toilet--even a Jabsco--can move bowl contents up to 6 linear feet and/or 4 vertical feet in the dry mode. And they stop pumping as soon as the bowl is empty. That works ok if the tank is below the the toilet--and you don't mind filling up your tank with flush water and/or leaving waste sitting in the head discharge line to permeate it...but not if the tank is above the toilet. Water runs downhill...so if you don't flush long enough in the dry mode to move the bowl contents ALL the way to the tank, it's gonna run back to the toilet. The joker valve will slow it down--at least a new one will...but even a brand new joker valve won't stop slow seepage...it's not supposed to. However, if the distance from the toilet to the tank is longer than 6', no toilet can move it all the way into the tank in the dry mode--OR the wet mode either...so replacing the toilet, even with a PH II, won't solve your problem. The only solution is a loop--not necessarily a vented loop--that's above the tank inlet fitting in the head discharge line close the to the toilet, so that it's only necessary to pump long enough to get the bowl contents over the top of it, then gravity will do the rest. So if your tank is within 6' of the toilet, all you need to do is flush long enough in the dry mode to move the bowl contents all the way into it. If it's more than 6' from the toilet, put a loop in the line that's above the top of the tank--or move the tank--and learn to flush longer in the dry mode. Not only will that solve your problem, but it should double or even triple the number of flushes your tank can hold. Btw...you say you have my book...but apparently you haven't read the chapter "Flush With Success" yet...'cuz everything I've said here is in that chapter.
Most boat owners don't know how to use the dry mode...they flush only in the wet mode except to move the last of the water out of the bowl...not realizing that any manual toilet--even a Jabsco--can move bowl contents up to 6 linear feet and/or 4 vertical feet in the dry mode. And they stop pumping as soon as the bowl is empty. That works ok if the tank is below the the toilet--and you don't mind filling up your tank with flush water and/or leaving waste sitting in the head discharge line to permeate it...but not if the tank is above the toilet. Water runs downhill...so if you don't flush long enough in the dry mode to move the bowl contents ALL the way to the tank, it's gonna run back to the toilet. The joker valve will slow it down--at least a new one will...but even a brand new joker valve won't stop slow seepage...it's not supposed to. However, if the distance from the toilet to the tank is longer than 6', no toilet can move it all the way into the tank in the dry mode--OR the wet mode either...so replacing the toilet, even with a PH II, won't solve your problem. The only solution is a loop--not necessarily a vented loop--that's above the tank inlet fitting in the head discharge line close the to the toilet, so that it's only necessary to pump long enough to get the bowl contents over the top of it, then gravity will do the rest. So if your tank is within 6' of the toilet, all you need to do is flush long enough in the dry mode to move the bowl contents all the way into it. If it's more than 6' from the toilet, put a loop in the line that's above the top of the tank--or move the tank--and learn to flush longer in the dry mode. Not only will that solve your problem, but it should double or even triple the number of flushes your tank can hold. Btw...you say you have my book...but apparently you haven't read the chapter "Flush With Success" yet...'cuz everything I've said here is in that chapter.
Peggie, thanks for all you do and your book
Even before your wrote the book, your contributions were great and accessible from this website and probably many more. We learned a lot from reading and IMPLEMENTING your recommendations. Keep up the good work. TEX: R E A D the B O O K.
Even before your wrote the book, your contributions were great and accessible from this website and probably many more. We learned a lot from reading and IMPLEMENTING your recommendations. Keep up the good work. TEX: R E A D the B O O K.
Thanks Peggy
Yes, I did read that section of your book and yes, we flush 20 - 30 times in order to move the waste all the way to the tank. The tank is more than 6' away from the toilet so a loop sounds like a solution but putting a loop in the system will be difficult due to the configuration of my boat. That is why I ask if you were familiar with my specific boat. It can be done but it looks like there will be some exposed drain pipe in the aft berth. Maybe some other Hunter 37.5 owners have some ideas. Tom S/V At Last
Yes, I did read that section of your book and yes, we flush 20 - 30 times in order to move the waste all the way to the tank. The tank is more than 6' away from the toilet so a loop sounds like a solution but putting a loop in the system will be difficult due to the configuration of my boat. That is why I ask if you were familiar with my specific boat. It can be done but it looks like there will be some exposed drain pipe in the aft berth. Maybe some other Hunter 37.5 owners have some ideas. Tom S/V At Last
dry mode flushing
Peggie, Help me understand this dry mode flushing. I am having a hard time understanding how the dry flush can move the liquid/solids through the line. It seems like the air used to push the contents through the line(in dry mode) would just bubble through the liquid in the line between the joker valve and the waste tank inlet if it is anything but downhill to the waste tank. To say it a second way, how can air be used to push liquid uphill at all. Seems like using water(wet flush) and the speed of flushing would be the only way to displace the urine/solids in the line(between joker valve and waste tank) with clean water. My particular boat has about an eight foot run that is a slow uphill run, I just imagine as I pump in dry mode most of the waste settles to the lowest point in the line. Before leaving the boat I pump quickly in wet mode to clear the contents of the line and replace them with clean water, but know I am introducing water that fills the tank quicker than I would like. Help me to understand the theory not so much my particular set up. Never have understood how it is possible. Anyone else that can help explain it in different ways might be good to help clear it up or determine it is not possible to clear the line without water. Looking forward to some different views on the issue, Mike
Peggie, Help me understand this dry mode flushing. I am having a hard time understanding how the dry flush can move the liquid/solids through the line. It seems like the air used to push the contents through the line(in dry mode) would just bubble through the liquid in the line between the joker valve and the waste tank inlet if it is anything but downhill to the waste tank. To say it a second way, how can air be used to push liquid uphill at all. Seems like using water(wet flush) and the speed of flushing would be the only way to displace the urine/solids in the line(between joker valve and waste tank) with clean water. My particular boat has about an eight foot run that is a slow uphill run, I just imagine as I pump in dry mode most of the waste settles to the lowest point in the line. Before leaving the boat I pump quickly in wet mode to clear the contents of the line and replace them with clean water, but know I am introducing water that fills the tank quicker than I would like. Help me to understand the theory not so much my particular set up. Never have understood how it is possible. Anyone else that can help explain it in different ways might be good to help clear it up or determine it is not possible to clear the line without water. Looking forward to some different views on the issue, Mike
example
An easy way to visualize is to imagine a drinking straw. Fill it partially full and blow through one end - out comes the water even if only partially full.
An easy way to visualize is to imagine a drinking straw. Fill it partially full and blow through one end - out comes the water even if only partially full.
Don the straw example
the straw example works because of the velocity of the air moving through the straw. Try it real slow like the pump on the head would, you should get some out but most will stay. thanks , Mike
the straw example works because of the velocity of the air moving through the straw. Try it real slow like the pump on the head would, you should get some out but most will stay. thanks , Mike
Clarification on the dry pumping
We don't dry pump in the sense that the bowl is dry but rather we add fresh water from the shower or a jug. I add enough water to fill to bowl 3/4 of the way full. It does move the waste away but I don't think it's really getting everything to the tank. I concerns me that there is back pressure occurring at the beginning of the pumping which shoots bowl containts up so it is imparitive that the toilet lid be closed or you will get a face full of s%$t.*yks We did not have that problem with the old pump. With the old pump you could hear an air sucking sound when the waste had reached the tank. Now I done hear that sound and I'm have this back flow problem. The new pump is sucking air after pumping 20-30 times but it doesn't sound the same. Tom S/V At Last
We don't dry pump in the sense that the bowl is dry but rather we add fresh water from the shower or a jug. I add enough water to fill to bowl 3/4 of the way full. It does move the waste away but I don't think it's really getting everything to the tank. I concerns me that there is back pressure occurring at the beginning of the pumping which shoots bowl containts up so it is imparitive that the toilet lid be closed or you will get a face full of s%$t.*yks We did not have that problem with the old pump. With the old pump you could hear an air sucking sound when the waste had reached the tank. Now I done hear that sound and I'm have this back flow problem. The new pump is sucking air after pumping 20-30 times but it doesn't sound the same. Tom S/V At Last
I wish I could do a live demo for y'all...
Mike, you don't need water to move water. If air couldn't move liquid, you couldn't blow out a line with an air compressor. Adding water just adds more water to the mix, it doesn't help to move the bowl contents. Pumping in the dry mode CAN move bowl contents through the line up to about 6 linear feet or 4 vertical feet. Further than that, the volume in the hose becomes too "thin" to move it much further. Slower more deliberate pumping moves liquids through the line MUCH more efficiently in either mode than fast pumping....fast pumping is what introduces air into the mix to interfere with moving it. So your fast pumping is self-defeating (and also wears out the rubber parts in the pump faster). Here's the right way to flush a manual toilet: ahead of use, pump just a couple of times in the wet mode to wet the bowl...after use, switch to dry mode to pump the bowl contents to the tank...then back to wet only long enough to bring in enough water to rinse the bowl and rinse out the line behind the waste...then back to dry to pump the rinse water to the tank. It WORKS!! And will double or even triple the number flush your tank can hold compared to pumping 20-30 x in the wet mode. Tom, the place to put the loop is in the head immediately after the toilet. You may have reroute the hose to minimize the amount that's exposed, which could be more effort than it's worth. The simpler solution: find a new location for the tank that's closer to the toilet. That MIGHT require a new tank, but it would solve several problems...venting, eliminating spilling out the vent when you're heeled etc, reduce the potential for permeated hoses. I suspect the backpressure/"spit up" when you first start pumping is caused by water or waste sitting in a low spot in the head discharge hose that's creating what amounts to a temporary blockage in the head discharge line. You get backpressure till you've pumped enough times to "break it up." I'd also check your tank vent for a blockage or partial blockage...'cuz an "air sucking" sound in the tank isn't normal. It's an indication that the tank is gasping for air through the toilet. The two most common places for vent blockages to occur are the thru-hull and the connection to the tank--both the fitting and that end of the vent line...due to waste spilling into it when the boat is heeled. I don't suppose you're planning to go the Annapolis sailboat show this weekend...'cuz I'll be there. I've been invited to give a seminar to the SSCA group on Saturday and decided to stick around through Monday to catch up with old friends and see how some of the new boats are plumbed. I'd be glad to sit down with anyone--or a group of you--someplace over a tall cool one and answer all your questions. So anyone reading this who's interested--or who'd just like to put faces with names--email me (I'm in all the owner directories) to swap cell #s.
Mike, you don't need water to move water. If air couldn't move liquid, you couldn't blow out a line with an air compressor. Adding water just adds more water to the mix, it doesn't help to move the bowl contents. Pumping in the dry mode CAN move bowl contents through the line up to about 6 linear feet or 4 vertical feet. Further than that, the volume in the hose becomes too "thin" to move it much further. Slower more deliberate pumping moves liquids through the line MUCH more efficiently in either mode than fast pumping....fast pumping is what introduces air into the mix to interfere with moving it. So your fast pumping is self-defeating (and also wears out the rubber parts in the pump faster). Here's the right way to flush a manual toilet: ahead of use, pump just a couple of times in the wet mode to wet the bowl...after use, switch to dry mode to pump the bowl contents to the tank...then back to wet only long enough to bring in enough water to rinse the bowl and rinse out the line behind the waste...then back to dry to pump the rinse water to the tank. It WORKS!! And will double or even triple the number flush your tank can hold compared to pumping 20-30 x in the wet mode. Tom, the place to put the loop is in the head immediately after the toilet. You may have reroute the hose to minimize the amount that's exposed, which could be more effort than it's worth. The simpler solution: find a new location for the tank that's closer to the toilet. That MIGHT require a new tank, but it would solve several problems...venting, eliminating spilling out the vent when you're heeled etc, reduce the potential for permeated hoses. I suspect the backpressure/"spit up" when you first start pumping is caused by water or waste sitting in a low spot in the head discharge hose that's creating what amounts to a temporary blockage in the head discharge line. You get backpressure till you've pumped enough times to "break it up." I'd also check your tank vent for a blockage or partial blockage...'cuz an "air sucking" sound in the tank isn't normal. It's an indication that the tank is gasping for air through the toilet. The two most common places for vent blockages to occur are the thru-hull and the connection to the tank--both the fitting and that end of the vent line...due to waste spilling into it when the boat is heeled. I don't suppose you're planning to go the Annapolis sailboat show this weekend...'cuz I'll be there. I've been invited to give a seminar to the SSCA group on Saturday and decided to stick around through Monday to catch up with old friends and see how some of the new boats are plumbed. I'd be glad to sit down with anyone--or a group of you--someplace over a tall cool one and answer all your questions. So anyone reading this who's interested--or who'd just like to put faces with names--email me (I'm in all the owner directories) to swap cell #s.
Our 37.5 experience...
As a past owner of a 1995 H37.5, I must admit to always being puzzled at how successfully the Jabsco head and the standard tank installation in that particular boat, worked so well. The original holding tank is located about 11 hose feet away from the head, and above it, by about 24" or so. Not sure how that worked, but it did. We never had a backflow problem or stuff hitting us in the face. We had the boat 10 years. The only problem we ever had was the original aluminum holding tank failing after 7 years. At that time, I ripped everything out and put in everything totally new. But I copied the original install down to the last hose, same size holding tank (but in poly) and an identical new Jabsco manual toilet. I figured it had worked so well for 7 years, I didn't want to touch the design. And it worked like a champ for another 3 years till we sold the boat. I mention all this Tom only as a word of encouragement about your current setup, assuming it's the original design. I know there are few options in that boat to relocate the tank. I would suspect the head/pump. Since you are so frustrated, it's worth trying a brand new head (not a rebuild). Cheap replacement in terms of other things we repair on boats. Only other thoughts: Did you replace the tank and if so, are the fittings in the same place as original? Also, the original vent line provided by Hunter is thin walled. Even tho you might be able to force some water through it with garden hose pressure, if there's a kink, it might prevent normal air movement. Look at it closely to make sure there is a clear run.
As a past owner of a 1995 H37.5, I must admit to always being puzzled at how successfully the Jabsco head and the standard tank installation in that particular boat, worked so well. The original holding tank is located about 11 hose feet away from the head, and above it, by about 24" or so. Not sure how that worked, but it did. We never had a backflow problem or stuff hitting us in the face. We had the boat 10 years. The only problem we ever had was the original aluminum holding tank failing after 7 years. At that time, I ripped everything out and put in everything totally new. But I copied the original install down to the last hose, same size holding tank (but in poly) and an identical new Jabsco manual toilet. I figured it had worked so well for 7 years, I didn't want to touch the design. And it worked like a champ for another 3 years till we sold the boat. I mention all this Tom only as a word of encouragement about your current setup, assuming it's the original design. I know there are few options in that boat to relocate the tank. I would suspect the head/pump. Since you are so frustrated, it's worth trying a brand new head (not a rebuild). Cheap replacement in terms of other things we repair on boats. Only other thoughts: Did you replace the tank and if so, are the fittings in the same place as original? Also, the original vent line provided by Hunter is thin walled. Even tho you might be able to force some water through it with garden hose pressure, if there's a kink, it might prevent normal air movement. Look at it closely to make sure there is a clear run.
One other question/thought
Since you replaced the hoses, are you sure there is no kink in the discharge hose from the head to the tank, where the hose does that very nasty tight 150 degree turn right behind the head? The hose disappears behind a wall there and in to the bottom of the hanging locker in the aft state-room. It's a bear to work new stiff hose (white hose) to do that bend when you replace the original soft black hoses. You can reach a hand in from the hanging locker to check all is OK there(no kinks).
Since you replaced the hoses, are you sure there is no kink in the discharge hose from the head to the tank, where the hose does that very nasty tight 150 degree turn right behind the head? The hose disappears behind a wall there and in to the bottom of the hanging locker in the aft state-room. It's a bear to work new stiff hose (white hose) to do that bend when you replace the original soft black hoses. You can reach a hand in from the hanging locker to check all is OK there(no kinks).
I'm with Mike ...
Everytime I winterize my pool, I have to use a 200 CFM shop vac, or compressed air to blow out my lines. In fact the lines are about the same size as those in my boats waste system. For my pool, when blowing out my skimmer line, it may take quite a while with the shop vac to get all the water out. You have to wait for it to sputter, bubble and mist the final bits of water out. If I have a weaker vac, it will take longer, or never be able to clear some of the water. I don't see why a marine head is much different. If you pump very slowly, surely the air will just bubble through the liquid in the hose and not push much liquid. As with my pool, I would expect that pumping (dry mode) faster must have a better chance at moving the liquid up the hose. The straw example, is not realistic in that the viscosity of water, the surface tension, and the meniscus formed have a stronger effect on the results that for hoses of the size we're interested. But surely, if you look at the extremes, and were to introduce a very very small amount of air (pumping very slowly, thus low CFM), it might never clear a hose of liquid. On the other hand, releasing the same volume of air very quickly (higher CFM) will surely do a better job. Maybe there's an upper limit, for a given pipe size, where exceeding a certain CFM wont have much further benefit, but the general rule seems like it should be that faster pumping is better? Chris
Everytime I winterize my pool, I have to use a 200 CFM shop vac, or compressed air to blow out my lines. In fact the lines are about the same size as those in my boats waste system. For my pool, when blowing out my skimmer line, it may take quite a while with the shop vac to get all the water out. You have to wait for it to sputter, bubble and mist the final bits of water out. If I have a weaker vac, it will take longer, or never be able to clear some of the water. I don't see why a marine head is much different. If you pump very slowly, surely the air will just bubble through the liquid in the hose and not push much liquid. As with my pool, I would expect that pumping (dry mode) faster must have a better chance at moving the liquid up the hose. The straw example, is not realistic in that the viscosity of water, the surface tension, and the meniscus formed have a stronger effect on the results that for hoses of the size we're interested. But surely, if you look at the extremes, and were to introduce a very very small amount of air (pumping very slowly, thus low CFM), it might never clear a hose of liquid. On the other hand, releasing the same volume of air very quickly (higher CFM) will surely do a better job. Maybe there's an upper limit, for a given pipe size, where exceeding a certain CFM wont have much further benefit, but the general rule seems like it should be that faster pumping is better? Chris
Hey Peggy, I'm just a helpful messenger
If it sounded like I'm condoning that sharp bend, I'm not. That's why I'm pointing it out to Tom as a potential trouble-spot. It existed in the original install by Hunter. He's trying to troubleshoot and no one else has pointed a finger at this bend yet. We have no idea what is on Tom's boat now at that bend since he has not described it to us and he has rehosed. My personal experience is it's near impossible to accomplish that bend with OdorSafe hose (without using radius fittings or heat) so I didn't do it that way when I rehosed my boat. But it is possible to do that bend with heat or, if you are really determined, a whole ton of force. I suspect it may be possible to do that bend with other "white" hose too, with difficulty. So someone may have done it that way on Tom's boat. We may not like the fact there's a bend there and it's inadvisable. But if it exists still, it may be contributing to Tom's current dilemma.
If it sounded like I'm condoning that sharp bend, I'm not. That's why I'm pointing it out to Tom as a potential trouble-spot. It existed in the original install by Hunter. He's trying to troubleshoot and no one else has pointed a finger at this bend yet. We have no idea what is on Tom's boat now at that bend since he has not described it to us and he has rehosed. My personal experience is it's near impossible to accomplish that bend with OdorSafe hose (without using radius fittings or heat) so I didn't do it that way when I rehosed my boat. But it is possible to do that bend with heat or, if you are really determined, a whole ton of force. I suspect it may be possible to do that bend with other "white" hose too, with difficulty. So someone may have done it that way on Tom's boat. We may not like the fact there's a bend there and it's inadvisable. But if it exists still, it may be contributing to Tom's current dilemma.
Thanks Brian and Peggy
Peggy, I wish I could be in Annapolis this weekend but unfortunately I have to work on my boat. Maybe you will make it to our In-The-Water Boat here in Kemah, TX one year and I'll buy you that tall cool one. You'll need it even in October down here. Brian, I like your ideas and will check the hose as I have not looked at it since it was installed, I will flush the vent line and thru hull fitting and if that is all good and it still doesn't work right I'll replace the whole damn toilet. Thanks for all the help. Tom S/V At Last
Peggy, I wish I could be in Annapolis this weekend but unfortunately I have to work on my boat. Maybe you will make it to our In-The-Water Boat here in Kemah, TX one year and I'll buy you that tall cool one. You'll need it even in October down here. Brian, I like your ideas and will check the hose as I have not looked at it since it was installed, I will flush the vent line and thru hull fitting and if that is all good and it still doesn't work right I'll replace the whole damn toilet. Thanks for all the help. Tom S/V At Last
Dry Pumping
When we bought a boat, who knew that we would have to learn about all of this disgusting stuff? After reading this thread, I have a few questions about continuing to pump with the lever set to "dry": Can you pump the waste beyond the vented loop? There is a 180-degree bend at that point and it's downhill after that. Does the waste hose from the vented loop down to the tank empty itself into the tank and fill with air to the level of waste in the tank? If dry pumping can move the waste past the vented loop and/or all the way to the holding tank, what remains in the hose - air? And where does it come from?? Something has to push the waste along, otherwise the hose would completely collapse when it was empty.
When we bought a boat, who knew that we would have to learn about all of this disgusting stuff? After reading this thread, I have a few questions about continuing to pump with the lever set to "dry": Can you pump the waste beyond the vented loop? There is a 180-degree bend at that point and it's downhill after that. Does the waste hose from the vented loop down to the tank empty itself into the tank and fill with air to the level of waste in the tank? If dry pumping can move the waste past the vented loop and/or all the way to the holding tank, what remains in the hose - air? And where does it come from?? Something has to push the waste along, otherwise the hose would completely collapse when it was empty.
Nancy, water runs downhill...
That's a basic law of physics. So there's no need to keep pumping longer than it takes to move the bowl contents over the top of the loop...'cuz once the bowl contents get over the top of the loop, gravity will keep it moving downhill into the tank. Unless the tank is full or the vent is blocked, creating backpressure that pushes back, the hose on the downhill side of the loop will empty itself of whatever is in it. If you stop by a boat store and take a look at sanitation hose, it should be obvious that it's much too stiff--and also reinforced with a helix--to collapse when it's empty. If it could, it would collapse on the shelf in the store. Learning how your system works and how to operate and maintain it isn't disgusting...disgusting is what can happen if you DON'T know how to operate and maintain it properly. So you might want to check out the link below...it'll take you to comprehensive "marine toilets and holding tanks 101" manual that should help you learn how to prevent something disgusting from happening.
That's a basic law of physics. So there's no need to keep pumping longer than it takes to move the bowl contents over the top of the loop...'cuz once the bowl contents get over the top of the loop, gravity will keep it moving downhill into the tank. Unless the tank is full or the vent is blocked, creating backpressure that pushes back, the hose on the downhill side of the loop will empty itself of whatever is in it. If you stop by a boat store and take a look at sanitation hose, it should be obvious that it's much too stiff--and also reinforced with a helix--to collapse when it's empty. If it could, it would collapse on the shelf in the store. Learning how your system works and how to operate and maintain it isn't disgusting...disgusting is what can happen if you DON'T know how to operate and maintain it properly. So you might want to check out the link below...it'll take you to comprehensive "marine toilets and holding tanks 101" manual that should help you learn how to prevent something disgusting from happening.
A possibility
On the "bubbling through" issue...Imagine a piece of hose, 4 feet vertical run, from bowl to top of a loop. the top of the loop if vented, and as such always at atmospheric pressure. If we pressurize the air on the bowl side, just slightly! It should begin moving the waste slowly up the tube. As long as it doesn't get disturbed, and the pressure is evenly pushing the waste, you'll get a siphon effect. You keep pumping in order to maintain this low pressure, as the air expends, but we don't want to make a big pressure difference or whip everythign up by pumping too fast! or else it'll bubble through. Perhaps a few pieces of marine TP is beneficial in creating this siphon effect, and it would work better that way than with just water?
On the "bubbling through" issue...Imagine a piece of hose, 4 feet vertical run, from bowl to top of a loop. the top of the loop if vented, and as such always at atmospheric pressure. If we pressurize the air on the bowl side, just slightly! It should begin moving the waste slowly up the tube. As long as it doesn't get disturbed, and the pressure is evenly pushing the waste, you'll get a siphon effect. You keep pumping in order to maintain this low pressure, as the air expends, but we don't want to make a big pressure difference or whip everythign up by pumping too fast! or else it'll bubble through. Perhaps a few pieces of marine TP is beneficial in creating this siphon effect, and it would work better that way than with just water?
vent lines
Peggie, Is the vent line generally very small in diameter? Pierre great presentation at the ssca
Peggie, Is the vent line generally very small in diameter? Pierre great presentation at the ssca
Pumping it through
Many of the boat's systems are still mysteries to me, but I am trying to understand them one at a time. This is what I gather from this thread so far - is this correct? After pumping waste and water through the head, the vertical hose to the vented loop is now full of liquid. By continuing to pump in the "dry" mode, air somehow pushes everything uphill through the loop and into the downhill hose. There can't be any siphon effect, because the purpose of the loop is to be a "siphon break". Now the uphill hose is empty (full of air) and the downhill hose empties itself into the holding tank. This almost makes sense, except for the concept of pumping air into the bottom of a vertical hose full of liquid and being able to move the contents out of the top. I am trying to visualize this using an image of clear hoses to be able to see what's going on (wouldn't that be a great science experiment for the kids?), but I still can't figure out why the air doesn't just bubble up instead of pushing the liquid the hose. How can you get more and more air underneath the liquid until the hose is empty?
Many of the boat's systems are still mysteries to me, but I am trying to understand them one at a time. This is what I gather from this thread so far - is this correct? After pumping waste and water through the head, the vertical hose to the vented loop is now full of liquid. By continuing to pump in the "dry" mode, air somehow pushes everything uphill through the loop and into the downhill hose. There can't be any siphon effect, because the purpose of the loop is to be a "siphon break". Now the uphill hose is empty (full of air) and the downhill hose empties itself into the holding tank. This almost makes sense, except for the concept of pumping air into the bottom of a vertical hose full of liquid and being able to move the contents out of the top. I am trying to visualize this using an image of clear hoses to be able to see what's going on (wouldn't that be a great science experiment for the kids?), but I still can't figure out why the air doesn't just bubble up instead of pushing the liquid the hose. How can you get more and more air underneath the liquid until the hose is empty?
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