Ok, I spent the weekend installing a new holding tank, and running the super extra heavy duty (expensive) hose from the head to the lazerette. The PO was discharging overboard, (grossly illegal) in more ways than one, and has the head seawater, and discharge pipe, plumbed through vented loops. At first I started mucking about with a 3 way valve, and I could see that I was going to have a head compartment full of a dog's breakfast of plumbing hose! So I have decided to scrap the 3 way valve idea. If ever I take my boat offshore, [NOT], I'll plumb it in. In the meatime, I'll put a brass plug in the ball valve seacock, and remove the handle. Do I still need the vented loop for sewage if I'm pumping directly back to the holding tank? Am I missing something? Does the vented loop have any other purpose, for my installation? The only thing I can think of is that the vented loop will maintian and air gap from the head to the tank, but why do I need this gap? I would like to keep everything as simple as possible, and if I can eliminate un-needed joints, extra fittings, pipe etc, then I'll be better off! Thanks for your thoughts! Eric
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Whether a loop is needed depends on whether
The tank inlet fitting is inboard or outboard. If it's outboard, a loop--though not necessarily vented--is recommended to prevent waste in the tank from running back to the toilet when the boat is heeled. If the inlet fitting is inboard, no loop is needed.
The tank inlet fitting is inboard or outboard. If it's outboard, a loop--though not necessarily vented--is recommended to prevent waste in the tank from running back to the toilet when the boat is heeled. If the inlet fitting is inboard, no loop is needed.
Inboard fitting
My holding tank is installed right up against the hull, and is curved to somewhat match the contour. The waste "in" is at the top, going in at a horizontal. I take it this means "inboard". It sits fairly high up to the deck, maybe a foot below. I guess if the tank were full, and the boat heeled over substantialy, there may be some backflow to the head. That would not be a nice thing. I think I'll leave the loop, since it's already there. Thanks for the speedy input Peggie!
Eric
My holding tank is installed right up against the hull, and is curved to somewhat match the contour. The waste "in" is at the top, going in at a horizontal. I take it this means "inboard". It sits fairly high up to the deck, maybe a foot below. I guess if the tank were full, and the boat heeled over substantialy, there may be some backflow to the head. That would not be a nice thing. I think I'll leave the loop, since it's already there. Thanks for the speedy input Peggie!
Ericloop
The loop is to prevent a siphon from being formed, and vented means vented. Unless you lead a line from the vent out through the hull, that's sewer gas you will be venting into the boat (no wonder so many people think holding tanks stink). If the tank is below the head then even if a siphon does occure it would only suck your potty dry. No big deal. With any through hull comming out below the water line a vented loop is a must. Still, especially on a holding tank system, run a vent line so that it is venting from out side the boat. Simple set up,tank below head, 1 1/2" from WC to inlet on holding tank, 1 1/2" line to Y valve, line 1 up to pump out fitting, line 2 to pump, then to vented loop then to through hull. The pump can be manuel or an electric mancerating pump (around $100). As far as your water in line, after the through hull go through a vented loop then to the WC. Some do it but don't plumb the intake water to your fresh water tanks. You don't want any chance of contaminating your pottable water. If your tank is above the head, it still can't create a vacume because the tank is vented, and the inlet is at the top of the tank. If the tank is above water line, by not using a vented loop on the #2 out line you could gravity drain the tank. Saves buying a pump, and vented loop, but then you must close both the Y and the through hull when not draining the tank. Since you have the through hull already, do it right so that it can be emptied off shore. You may cruise some where where you can't get pumped out and the trip off shore would be shorter than the trip to the next pump out. It will add value to your boat.
The loop is to prevent a siphon from being formed, and vented means vented. Unless you lead a line from the vent out through the hull, that's sewer gas you will be venting into the boat (no wonder so many people think holding tanks stink). If the tank is below the head then even if a siphon does occure it would only suck your potty dry. No big deal. With any through hull comming out below the water line a vented loop is a must. Still, especially on a holding tank system, run a vent line so that it is venting from out side the boat. Simple set up,tank below head, 1 1/2" from WC to inlet on holding tank, 1 1/2" line to Y valve, line 1 up to pump out fitting, line 2 to pump, then to vented loop then to through hull. The pump can be manuel or an electric mancerating pump (around $100). As far as your water in line, after the through hull go through a vented loop then to the WC. Some do it but don't plumb the intake water to your fresh water tanks. You don't want any chance of contaminating your pottable water. If your tank is above the head, it still can't create a vacume because the tank is vented, and the inlet is at the top of the tank. If the tank is above water line, by not using a vented loop on the #2 out line you could gravity drain the tank. Saves buying a pump, and vented loop, but then you must close both the Y and the through hull when not draining the tank. Since you have the through hull already, do it right so that it can be emptied off shore. You may cruise some where where you can't get pumped out and the trip off shore would be shorter than the trip to the next pump out. It will add value to your boat.
Common misconception about vented loops
A vented loop should not allow anything to escape OUT the vent...It should only allow air to be pulled INTO the line to break a siphon. A vented loop only squirts liquid or gasses when the air valve is missing or has failed. If you have a typical PVC vented loop, look closely at the hole in the nipple on the top of the loop...you'll see that it's threaded...that's where the air valve goes. But because air valves are replaceable, they're often sold separately...so owners who aren't knowledgable about vented loops don't know they need one. Bronze and more expensive PVC vented loops may have a "cap" type air valve. Running a vent line off a vented loop is a bad idea, because the hose is so small--typically just 1/4" that it quickly becomes clogged with waste and/or sea water minerals, turning it into an UNvented loop that no longer has any ability to break a siphon. And because it's also "out of sight, out of mind," it's never cleaned out...whereas an air valve will let you know when it needs cleaning or replacement. It's HIGHLY unlikely that any siphon can occur in in a line between the toilet and the tank. Siphons only occur in lines through liquid is being PULLED...they cannot occur in a line through which water is being pushed. Since waste in a tank would be pushing back toward the head, a vented loop isn't needed. The only thing that is needed is a loop that's higher than the waste can be pushed over... Eric, "inboard" is toward the centerline of the boat..."outboard" is toward the hull. So for your inlet fitting to be inboard on the tank it would have to be either on a vertical surface that's on the opposite side of the tank from the hull, or on part of the the top of the tank that's closest to the centerline, not next to the hull. And btw, when the vent fitting is inboard on the tank, it prevents waste in the tank from spilling out the vent when the boat is heeled.
A vented loop should not allow anything to escape OUT the vent...It should only allow air to be pulled INTO the line to break a siphon. A vented loop only squirts liquid or gasses when the air valve is missing or has failed. If you have a typical PVC vented loop, look closely at the hole in the nipple on the top of the loop...you'll see that it's threaded...that's where the air valve goes. But because air valves are replaceable, they're often sold separately...so owners who aren't knowledgable about vented loops don't know they need one. Bronze and more expensive PVC vented loops may have a "cap" type air valve. Running a vent line off a vented loop is a bad idea, because the hose is so small--typically just 1/4" that it quickly becomes clogged with waste and/or sea water minerals, turning it into an UNvented loop that no longer has any ability to break a siphon. And because it's also "out of sight, out of mind," it's never cleaned out...whereas an air valve will let you know when it needs cleaning or replacement. It's HIGHLY unlikely that any siphon can occur in in a line between the toilet and the tank. Siphons only occur in lines through liquid is being PULLED...they cannot occur in a line through which water is being pushed. Since waste in a tank would be pushing back toward the head, a vented loop isn't needed. The only thing that is needed is a loop that's higher than the waste can be pushed over... Eric, "inboard" is toward the centerline of the boat..."outboard" is toward the hull. So for your inlet fitting to be inboard on the tank it would have to be either on a vertical surface that's on the opposite side of the tank from the hull, or on part of the the top of the tank that's closest to the centerline, not next to the hull. And btw, when the vent fitting is inboard on the tank, it prevents waste in the tank from spilling out the vent when the boat is heeled.
inny, outty,
Hi Peggie. I'm sure we are talking about the same thing, on the inboard/outboard issue! Like you described my tank > waste in, is through a vertically installed fitting, where the pipe is running horizontal, as is the vent out. Both face inboard. The 1/2' vent loops up and out to the hull fitting, and the waste out, is fitted on top of the tank, on a horizontal plane, piped almost straight up to the deck fitting. My tank is higher than the head. I reasoned below about keeping the waste loop installed, that should there ever be an occasion where the tank is full, and I heel over substantially, waste might backflow into the waste hose, and migrate toward the head. Probably never really happen, but one never knows. If there was a backflow, this flow will never make it to the head with the loop in place. It's probably overkill, and as you pointed out not needed, but since I have it! Greg, thanks for your comments. I'm scrapping the idea of the 3 way valve, since I sail on the Great Lakes. I'll probably go even further "inland" in the future, as I intend on moving up to Midland, on Georgian Bay! I am a believer in doing things right, and once, but for me to put in all the extra material for overboard discharge, something that is illegal to use, it's not going to happen Happy sailing! Cheers Eric
Hi Peggie. I'm sure we are talking about the same thing, on the inboard/outboard issue
! Like you described my tank > waste in, is through a vertically installed fitting, where the pipe is running horizontal, as is the vent out. Both face inboard. The 1/2' vent loops up and out to the hull fitting, and the waste out, is fitted on top of the tank, on a horizontal plane, piped almost straight up to the deck fitting. My tank is higher than the head. I reasoned below about keeping the waste loop installed, that should there ever be an occasion where the tank is full, and I heel over substantially, waste might backflow into the waste hose, and migrate toward the head. Probably never really happen, but one never knows. If there was a backflow, this flow will never make it to the head with the loop in place. It's probably overkill, and as you pointed out not needed, but since I have it! Greg, thanks for your comments. I'm scrapping the idea of the 3 way valve, since I sail on the Great Lakes. I'll probably go even further "inland" in the future, as I intend on moving up to Midland, on Georgian Bay! I am a believer in doing things right, and once, but for me to put in all the extra material for overboard discharge, something that is illegal to use, it's not going to happen Happy sailing! Cheers Eric- Status