At the top of the anti-siphon loop in my raw water intake circuit, there is a 1/4' plastic tube attached which leads to the bilge. When the engine is running, at least one gallon per hour flows through the tube and into the bilge. Is this normal and if not what could be causing it to flow this much? The engine is a 50hp VolvoPenta. Thanks in advance. Peter Milne S/V Blue Heron
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That's too much...
Some valves dribble a bit which is what that little hose is for but 1 gal/hr. sounds like way too much. Makes me wonder if the valve is functional at all. You might try blowing it out with some air or cleaning it up and see if that helps. If not they aren't hard or expensive to replace...
Some valves dribble a bit which is what that little hose is for but 1 gal/hr. sounds like way too much. Makes me wonder if the valve is functional at all. You might try blowing it out with some air or cleaning it up and see if that helps. If not they aren't hard or expensive to replace...
It will be
expensive, but you probably should replace the vented loop. The vent is just that, when you run your engine the valve should close, no water should come out, when you shut down, the valve opens, allowing the remaining water to safely flow out instead of into the engine.
expensive, but you probably should replace the vented loop. The vent is just that, when you run your engine the valve should close, no water should come out, when you shut down, the valve opens, allowing the remaining water to safely flow out instead of into the engine.
Proper Vented Loops DON't leak
You should NOT have ANY water entering through the vented loop assembly! The small hose from the apex of the loop should be led upwards (as high as possible), which increases the effective height of the loop above waterline - not down into bilge. You probably don’t have a siphon-break on the loop fitting, so get that 1/4" hose led and fixed up high, and (perhaps) add an anti-siphon device to it’s open end. From Forespar: http://www.forespar.com/catalog/plumbing/ventloop.htm Vented Loop installations ensure that fluids will not siphon from tank to tank. Vented loops are commonly used in the marine toilet system and engine cooling system. The simple duckbill one-way valve system incorporated in the top of the loop allows air to enter the line when not in use, yet effectively seals as water or other fluid passes through. Precision molded in high-strength non-corrosive Marelon®, neither vent nor loop will corrode. The duckbill one-way valve is designed to seal properly if particulate matter is present in fluids. The optional Vent Barb allows venting to the outside of the hull via a 1/4" tube. HTH Gord
You should NOT have ANY water entering through the vented loop assembly! The small hose from the apex of the loop should be led upwards (as high as possible), which increases the effective height of the loop above waterline - not down into bilge. You probably don’t have a siphon-break on the loop fitting, so get that 1/4" hose led and fixed up high, and (perhaps) add an anti-siphon device to it’s open end. From Forespar: http://www.forespar.com/catalog/plumbing/ventloop.htm Vented Loop installations ensure that fluids will not siphon from tank to tank. Vented loops are commonly used in the marine toilet system and engine cooling system. The simple duckbill one-way valve system incorporated in the top of the loop allows air to enter the line when not in use, yet effectively seals as water or other fluid passes through. Precision molded in high-strength non-corrosive Marelon®, neither vent nor loop will corrode. The duckbill one-way valve is designed to seal properly if particulate matter is present in fluids. The optional Vent Barb allows venting to the outside of the hull via a 1/4" tube. HTH Gord
Try Nigel Calder
Hi Peter, My copy of Nigel Calder's Marine Diesel Engines is on the boat and not accessible right now. However, my recollection of his advice on this subject is that the anti ciphon valve needs to be cleaned periodically by disassembling it and rinsing it in very warm water. It may be there is a salt buildup on the valve that is preventing it from seating properly when the engine is running and causing the overflow into the bilge. Hope this helps. Gary Wyngarden S/V Wanderlust H37.5
Hi Peter, My copy of Nigel Calder's Marine Diesel Engines is on the boat and not accessible right now. However, my recollection of his advice on this subject is that the anti ciphon valve needs to be cleaned periodically by disassembling it and rinsing it in very warm water. It may be there is a salt buildup on the valve that is preventing it from seating properly when the engine is running and causing the overflow into the bilge. Hope this helps. Gary Wyngarden S/V Wanderlust H37.5
Anti siphon
If you take a look around you'll notice that about 1/3 of the anti siphon loops for engines these days come direct from the factory with a hose attachment. This is because they always start to leak at some time. The concern is the opposite, i.e. that the loop will plug/freeze in the closed position. The problem that you have is that the hose should be up and led to a scupper. Putting it into the bilge completely defeats the purpose. I figure I'll get a little flack about this comment so I'll ask that you research it a little. You'll find that anti siphon setups include a siphon break valve which is what you had, and a siphon break tee. What you have now with the water running through is a tee. When my vent started to leak 2 qualified marine surveyors told me to run it to a scupper. I was told not to loop it up and down, but rather continuous flow, or could be tapped into the exhaust hose after the silencer assuming it would be high enough (not on mine). Well, that should stir comments. Peter
If you take a look around you'll notice that about 1/3 of the anti siphon loops for engines these days come direct from the factory with a hose attachment. This is because they always start to leak at some time. The concern is the opposite, i.e. that the loop will plug/freeze in the closed position. The problem that you have is that the hose should be up and led to a scupper. Putting it into the bilge completely defeats the purpose. I figure I'll get a little flack about this comment so I'll ask that you research it a little. You'll find that anti siphon setups include a siphon break valve which is what you had, and a siphon break tee. What you have now with the water running through is a tee. When my vent started to leak 2 qualified marine surveyors told me to run it to a scupper. I was told not to loop it up and down, but rather continuous flow, or could be tapped into the exhaust hose after the silencer assuming it would be high enough (not on mine). Well, that should stir comments. Peter
look at this
I've been pretending for a while that I can buy a newer bigger boat. I have notice in looking at a number of boats on the net, ( mostly Beneteau's ) that they do have a hose from the siphon down ( it looks like ) to the bilge. Always struck me as strange. Aslo I remember reading ( i thought at yanmarhelp.com, but couldn't find today ) that there are some loops that don't have a valve, so it won't clog. They just allow a small stream of water to discharge. Still it needs to be open to the air high above the waterline. http://www.yachtworld.com/core/listing/pl_display_photo.jsp?slim=quick&&photo=2&boat_id=1138539&boatname=Beneteau+411&photo_name=Engine
I've been pretending for a while that I can buy a newer bigger boat. I have notice in looking at a number of boats on the net, ( mostly Beneteau's ) that they do have a hose from the siphon down ( it looks like ) to the bilge. Always struck me as strange. Aslo I remember reading ( i thought at yanmarhelp.com, but couldn't find today ) that there are some loops that don't have a valve, so it won't clog. They just allow a small stream of water to discharge. Still it needs to be open to the air high above the waterline. http://www.yachtworld.com/core/listing/pl_display_photo.jsp?slim=quick&&photo=2&boat_id=1138539&boatname=Beneteau+411&photo_name=Engine
Geez, I don't know. I don't like that set up.
Seems to me that that hose is almost defeating the purpose of an "Air above the water line" siphon break. It sounds as if water is siphoning into the bilge. 1 gallon an hour isn't trivial. I understand the theory that if it 'does' leak a bit it goes into the bilge, but what if you get a complete "siphon" going from the water below your boat up the raw water hose and down that little overflow tube. Seems like it will siphon water into my boat in the right circumstances. I like how my boat is set up. I have a siphon break but no hose. If it does leak its just a bit of water in my lazarrete. But so far I have had no problems with it.
Seems to me that that hose is almost defeating the purpose of an "Air above the water line" siphon break. It sounds as if water is siphoning into the bilge. 1 gallon an hour isn't trivial. I understand the theory that if it 'does' leak a bit it goes into the bilge, but what if you get a complete "siphon" going from the water below your boat up the raw water hose and down that little overflow tube. Seems like it will siphon water into my boat in the right circumstances. I like how my boat is set up. I have a siphon break but no hose. If it does leak its just a bit of water in my lazarrete. But so far I have had no problems with it.
Good point Tom...
I suppose the drain tube coming from the anti-siphon valve might in fact turn into a siphon under the right set of circumstances. Wouldn't THAT be ironic... Better be sure the end of the tube isn't below the waterline which it probably is if it's draining into the bilge. Better yet go get a new valve.
I suppose the drain tube coming from the anti-siphon valve might in fact turn into a siphon under the right set of circumstances. Wouldn't THAT be ironic... Better be sure the end of the tube isn't below the waterline which it probably is if it's draining into the bilge. Better yet go get a new valve.
Pardon my ignorance but...
...why have a vacumn breaker in a closed system anyway? I can understand the head loop perhaps better with an 'open' ended potential of the stool and the joker valve getting blocked open, etc., but whats to fail and create a problem with the engine cooling lines short of a thru-hull coming loose...in which case, the loop will be moot. No one that I am aware of has one in their system...and it seems to be a great way to get an air lock and run the impeller to oblivion.
...why have a vacumn breaker in a closed system anyway? I can understand the head loop perhaps better with an 'open' ended potential of the stool and the joker valve getting blocked open, etc., but whats to fail and create a problem with the engine cooling lines short of a thru-hull coming loose...in which case, the loop will be moot. No one that I am aware of has one in their system...and it seems to be a great way to get an air lock and run the impeller to oblivion.
wet exhaust
Dale, it forms part of the wet exhaust and it's there to prevent water from siphoning back from the waterlift and/or from the outside (depending on your setup) and even prevent water from siphoning from the raw water intake and filling up your engine. It is not only common practice, but a good recommendation if your engine is below the waterline, which is typical on most sailboats. If you have a dry exhaust or your engine is above the waterline this is not necessary. Peter
Dale, it forms part of the wet exhaust and it's there to prevent water from siphoning back from the waterlift and/or from the outside (depending on your setup) and even prevent water from siphoning from the raw water intake and filling up your engine. It is not only common practice, but a good recommendation if your engine is below the waterline, which is typical on most sailboats. If you have a dry exhaust or your engine is above the waterline this is not necessary. Peter
Dale, My Yanmar manual said to install a vented
loop if the engine is located below the waterline. The factory did install one. (H34) It spit a little water now and then and had to be maintained with regular cleaning. When I rebuilt my boat, I could think of NO reason to re-install it. Good riddance. No problems now.
loop if the engine is located below the waterline. The factory did install one. (H34) It spit a little water now and then and had to be maintained with regular cleaning. When I rebuilt my boat, I could think of NO reason to re-install it. Good riddance. No problems now.
remove the loop
I agree with Fred. It seems unlikely that raw sea water is going to fill up the engine with the water pump impler in the way. However, if you like you can install another shut off valve before the engine as I have. It will ensure that sea water does not enter the boat. In addition, I put in a second valve and hose system to the nearest fresh water sink drain (valve there too). In my case this was the head sink. This allows a fresh water flush of the engine after every use which has got to be good for the engine. If the raw sea water is used to cool the fresh water engine system, put the shut off valve in front of the cooling box. Of course shutting the thru hull valve off solves all problems.
I agree with Fred. It seems unlikely that raw sea water is going to fill up the engine with the water pump impler in the way. However, if you like you can install another shut off valve before the engine as I have. It will ensure that sea water does not enter the boat. In addition, I put in a second valve and hose system to the nearest fresh water sink drain (valve there too). In my case this was the head sink. This allows a fresh water flush of the engine after every use which has got to be good for the engine. If the raw sea water is used to cool the fresh water engine system, put the shut off valve in front of the cooling box. Of course shutting the thru hull valve off solves all problems.
Raw Water Intake vs. Exhaust Loop.....
My confusion lay with the original post (and no clarification), which stated: "...At the top of the anti-siphon loop in my raw water intake circuit,". On the other hand, I don't have a vent in the wet-lift muffler either, but the loop rises to the bottom of the cockpit floor and so don't anticipate a problem there either, even with following seas... (Paul,) its a little late in life for my '79 Yanmar to sweat a little build up in the water jacket so don't anticipate many mods in the flush department but a good idea for a re-power. Thanks all, Peter/Fred/Paul
My confusion lay with the original post (and no clarification), which stated: "...At the top of the anti-siphon loop in my raw water intake circuit,". On the other hand, I don't have a vent in the wet-lift muffler either, but the loop rises to the bottom of the cockpit floor and so don't anticipate a problem there either, even with following seas... (Paul,) its a little late in life for my '79 Yanmar to sweat a little build up in the water jacket so don't anticipate many mods in the flush department but a good idea for a re-power. Thanks all, Peter/Fred/Paul
I think yours is shot.
Peter: I think your vented loop is shot. I suggest that you look at the Vetus Marine engine loops. They have a couple of models. One with a hose and another without. The down side of having one without the hose is that the seawater is going to corrode your engine (like it probably is already doing).
Peter: I think your vented loop is shot. I suggest that you look at the Vetus Marine engine loops. They have a couple of models. One with a hose and another without. The down side of having one without the hose is that the seawater is going to corrode your engine (like it probably is already doing).
It Might Just Save Your Engine
The vented loop on the raw water pump intake is to prevent a siphon condition from drawing water from the thru haul, through the raw water pump through the heat exchanger into the water lift muffler. The water would then fill the water lift muffler forcing the water up the engine exhaust into the cylinders. PS: Vented Loops are designed to let air in when a siphon condition exist to break the siphon. When properly maintained, no fluid or oders should come from them.
The vented loop on the raw water pump intake is to prevent a siphon condition from drawing water from the thru haul, through the raw water pump through the heat exchanger into the water lift muffler. The water would then fill the water lift muffler forcing the water up the engine exhaust into the cylinders. PS: Vented Loops are designed to let air in when a siphon condition exist to break the siphon. When properly maintained, no fluid or oders should come from them.
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