I know this is going to sound like the most lame, uninformed question, but what is the purpose of the 'vented loop' Am currently in process of installing toilet/tank in a '77 C-25 and keep hearing conflicting reports of the need for a 'vented loop' I understand the part about it needing to be at or above the waterline, and that it should prevent back-flow, but..... if it is VENTED why spend big $$$ on odor resistant plumbing tubing, and if your head is working properly, won't all the waste be forced into the tank anyway ?? What am I missing here ??? Was hoping the Mistress could enlighten Richard C '77 C-25 SR/FK (waiting for a name)
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If you are speaking of the vented loop for the ..
intake, then the vented loop breaks the flow of water into the toilet after you have completed the flush. If the toilet is mounted below the water line and if someone using it fails to set the pump lever to "dry bowl", then it could continue to fill with fresh water and overflow and continue to do so until the boat sinks. Mine is mounted low enough that it will do that, happened to me with a guess onboard who left the lever on the toilet to flush position and it filled all night long til I discovered it the next morning. I installed a vented loop on the intake hose mounted higher than the waterline of the boat, now, it breaks the vacume so water does not continue to flow in no matter which position the lever is set.
intake, then the vented loop breaks the flow of water into the toilet after you have completed the flush. If the toilet is mounted below the water line and if someone using it fails to set the pump lever to "dry bowl", then it could continue to fill with fresh water and overflow and continue to do so until the boat sinks. Mine is mounted low enough that it will do that, happened to me with a guess onboard who left the lever on the toilet to flush position and it filled all night long til I discovered it the next morning. I installed a vented loop on the intake hose mounted higher than the waterline of the boat, now, it breaks the vacume so water does not continue to flow in no matter which position the lever is set.
Vented loop serves two functions
Neither of which have ANYthing to do with venting your holding tank. A vented loop goes in hoses connected to thru-hulls below the waterline, and prevents water OUTtside the boat from seeking its own level INside the boat through any open hole in the boat below the waterline. It does that two ways: a one-way valve that only allows air INto the line--shouldn't let air or anything else out--creates an air break in the hose that prevents a siphon from forming. Because it should be isntalled at least 8-12" above the waterline at any angle of hell, it also creates an arch in the hose too high above the waterline for water (or tank contents) to climb over. It won't stop anything that's being pushed over it from the toilet, or water forced up a hose by the pressure of the hull against the water against the hull by the movement of the boat (and effect known as "ram water") through a thru-hull that shouldn't have been left open...it's strictly passive, intended to keep water outside the boat from rising inside your boat high enough to sink it. Vented loops belong in any hose connected to a below-waterline thru-hull. Whether one is needed between the toilet and a tank depends the individual installation.
Neither of which have ANYthing to do with venting your holding tank. A vented loop goes in hoses connected to thru-hulls below the waterline, and prevents water OUTtside the boat from seeking its own level INside the boat through any open hole in the boat below the waterline. It does that two ways: a one-way valve that only allows air INto the line--shouldn't let air or anything else out--creates an air break in the hose that prevents a siphon from forming. Because it should be isntalled at least 8-12" above the waterline at any angle of hell, it also creates an arch in the hose too high above the waterline for water (or tank contents) to climb over. It won't stop anything that's being pushed over it from the toilet, or water forced up a hose by the pressure of the hull against the water against the hull by the movement of the boat (and effect known as "ram water") through a thru-hull that shouldn't have been left open...it's strictly passive, intended to keep water outside the boat from rising inside your boat high enough to sink it. Vented loops belong in any hose connected to a below-waterline thru-hull. Whether one is needed between the toilet and a tank depends the individual installation.
Hey, Peggy, what's an angle of hell???
It doesn't get that hot around the head on my boat... ;>) Tom
It doesn't get that hot around the head on my boat... ;>) Tom
Angle of hell:
What a boat heeled 30 degrees is to a spouse, SO or other passenger who becomes terrified at any angle greater than 10 degrees.
What a boat heeled 30 degrees is to a spouse, SO or other passenger who becomes terrified at any angle greater than 10 degrees.
Put the loop...
...on the line between the pump outlet and the bowl of the toilet, NOT between the seacock and the pump mechanism. This is what my Jabsco instruction manual says: "if the toilet is, or can be, below the waterline at any normal (including static) attitude of vessel heel and/or trim, a 3/4" vented loop must be installed in a length of hose connecting the flushing pump to the rear of the bowl" I suspect this has something to do with the way the water is "driven" in the two hoses. In the inlet, water is 'sucked' to the pump from the seacock, whereas between the pump and bowl it is pumped under pressure. The anti-siphon valve probably does not work properly when water is drawn from it rather than pumped through it. Also, if you are installing a dump valve (via a Y-valve), you must also use a vented loop in the discharge line that goes from the y-valve to the through-hull discharge. Cheers, Tim
...on the line between the pump outlet and the bowl of the toilet, NOT between the seacock and the pump mechanism. This is what my Jabsco instruction manual says: "if the toilet is, or can be, below the waterline at any normal (including static) attitude of vessel heel and/or trim, a 3/4" vented loop must be installed in a length of hose connecting the flushing pump to the rear of the bowl" I suspect this has something to do with the way the water is "driven" in the two hoses. In the inlet, water is 'sucked' to the pump from the seacock, whereas between the pump and bowl it is pumped under pressure. The anti-siphon valve probably does not work properly when water is drawn from it rather than pumped through it. Also, if you are installing a dump valve (via a Y-valve), you must also use a vented loop in the discharge line that goes from the y-valve to the through-hull discharge. Cheers, Tim
How it works
A vented loop has a one-way valve in it (at least it's supposed to...if there's only a nipple at the top that has a hole in it, the air valve is missing) that allows air into the line to break a siphon, but shouldn't let air--or anything else--out. If a vented loop were installed between the thru-hull and the pump, it would interfere with the pump's ability to prime...the pump would just pull in air through the air valve. But a vented loop can't stop water or waste from being pushed over it, so it has to go between the pump and the bowl because the pump is no longer pulling water, but pushing it out. On almost all manual toilets, there's a short piece of 3/4" hose that connects the pump to the back of the bowl...that hose has to be removed and replaced with two pieces of hose long enough mount a vented loop above the toilet that's at least 8-12" above the waterline at any angle of heel (or hell, as the case may be<g>). It's also necessary to install a vented loop in any hose connected to a below-waterline through-hull--direct toilet discharge and/or tank dump through hull...same "rules" apply--at least 8-12" above the waterline at any angle of heel. A vented loop in the line does NOT mean that the thru-hull can be left open while underway. CG and ABYC safety standards call for keeping all seacocks closed except when actually in use and therefore readily accessible. However, because today's boat buyer considers decor more important than safety, boat builders ignore the standard and put them in locations that makes it all but impossible to open and close them as needed. The solution: shut-off valves inline in the head intake hose and any head discharge hose that goes directly overboard that are in readily accessible locations. Keep those valves closed except when the toilet is actually in use. Don't even THINK of relying on the dry/flush valve in the toilet...not only do those valves, especially in Jabsco toilets, have a VERY high failure rate, but people are all too prone to leave 'em in the wrong position.
A vented loop has a one-way valve in it (at least it's supposed to...if there's only a nipple at the top that has a hole in it, the air valve is missing) that allows air into the line to break a siphon, but shouldn't let air--or anything else--out. If a vented loop were installed between the thru-hull and the pump, it would interfere with the pump's ability to prime...the pump would just pull in air through the air valve. But a vented loop can't stop water or waste from being pushed over it, so it has to go between the pump and the bowl because the pump is no longer pulling water, but pushing it out. On almost all manual toilets, there's a short piece of 3/4" hose that connects the pump to the back of the bowl...that hose has to be removed and replaced with two pieces of hose long enough mount a vented loop above the toilet that's at least 8-12" above the waterline at any angle of heel (or hell, as the case may be<g>). It's also necessary to install a vented loop in any hose connected to a below-waterline through-hull--direct toilet discharge and/or tank dump through hull...same "rules" apply--at least 8-12" above the waterline at any angle of heel. A vented loop in the line does NOT mean that the thru-hull can be left open while underway. CG and ABYC safety standards call for keeping all seacocks closed except when actually in use and therefore readily accessible. However, because today's boat buyer considers decor more important than safety, boat builders ignore the standard and put them in locations that makes it all but impossible to open and close them as needed. The solution: shut-off valves inline in the head intake hose and any head discharge hose that goes directly overboard that are in readily accessible locations. Keep those valves closed except when the toilet is actually in use. Don't even THINK of relying on the dry/flush valve in the toilet...not only do those valves, especially in Jabsco toilets, have a VERY high failure rate, but people are all too prone to leave 'em in the wrong position.
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