While planning to replace a bladder system I have everything (I think) considered except the location of the vented loop fittings...if I even need them. I have read several articles and it seems that each article bring a new location to add one. For a simple holding tank system I have three vented loops! Can someone explain the necessity of a vented loop and where they REALLY are needed. Thanks in Advance - Doug
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Peggie Hall/HeadMistress
Vented loops...
A vented loop serves two purposes, both of which are intended to prevent water outside the boat from seeking its own level inside the boat and sinking the boat: it breaks a siphon, and it creates an arch in the line above the waterline. How many are needed depends on several things. If the toilet is at or below the waterline, a vented loop in the head intake (between the pump and the bowl, not between the thru-hull and the pump) is needed to prevent sea water from flooding and overflowing the bowl. If the toilet is plumbed to discharge directly overboard at sea, a vented loop is needed in the head discharge line between the y-valve and the thru-hull...if the toilet ONLY flushes into the tank, none is needed. If the tank can be dumped at sea through a below-waterline thru-hull, a vented loop is needed between the macerator (or manual pump) and the thru-hull.
A vented loop serves two purposes, both of which are intended to prevent water outside the boat from seeking its own level inside the boat and sinking the boat: it breaks a siphon, and it creates an arch in the line above the waterline. How many are needed depends on several things. If the toilet is at or below the waterline, a vented loop in the head intake (between the pump and the bowl, not between the thru-hull and the pump) is needed to prevent sea water from flooding and overflowing the bowl. If the toilet is plumbed to discharge directly overboard at sea, a vented loop is needed in the head discharge line between the y-valve and the thru-hull...if the toilet ONLY flushes into the tank, none is needed. If the tank can be dumped at sea through a below-waterline thru-hull, a vented loop is needed between the macerator (or manual pump) and the thru-hull.
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John Visser
more questions
Thanks Peggy, good answer. I have had the same thoughts and concerns about the need for vented loops. The only ones I'm aware of on my C36 are the shower sump to overboard drain seacock line, and the raw water pump to heat exchanger line. I don't have a vented loop on the pump to bowl line. Do I need one on a C36? Also, I'm planning on adding a Forespar raw water strainer for the engine raw water. The instructions say to mount the strainer 12" above the static water line, "if possible." Can you commetn on installing such things? Thanks, jv
Thanks Peggy, good answer. I have had the same thoughts and concerns about the need for vented loops. The only ones I'm aware of on my C36 are the shower sump to overboard drain seacock line, and the raw water pump to heat exchanger line. I don't have a vented loop on the pump to bowl line. Do I need one on a C36? Also, I'm planning on adding a Forespar raw water strainer for the engine raw water. The instructions say to mount the strainer 12" above the static water line, "if possible." Can you commetn on installing such things? Thanks, jv
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Peggie Hall/HeadMistress
If your toilet is manual and below the waterline
You need a vented loop in the head intake, 'cuz relying on the wet/dry valve to keep water outside the boat from seeking its own level inside the boat when you're not there--and even when you are--is a good way to sink a boat. In fact, open head seacocks are the #1 cause of boats sinking in their slips. Vented loops should be 8-12" above the waterline at any angle of heel. Strainers, otoh, have have to be installed up to 12" above the static waterline (waterline while the boat is at rest) to allow the strainer to be removed for cleaning without taking on water...which means they should also be readily accessible. If you need a strainer on the engine water intake, I suggest you also put on the head intake, also in an accessible location. The strainer does go between the thru-hull and the pump.
You need a vented loop in the head intake, 'cuz relying on the wet/dry valve to keep water outside the boat from seeking its own level inside the boat when you're not there--and even when you are--is a good way to sink a boat. In fact, open head seacocks are the #1 cause of boats sinking in their slips. Vented loops should be 8-12" above the waterline at any angle of heel. Strainers, otoh, have have to be installed up to 12" above the static waterline (waterline while the boat is at rest) to allow the strainer to be removed for cleaning without taking on water...which means they should also be readily accessible. If you need a strainer on the engine water intake, I suggest you also put on the head intake, also in an accessible location. The strainer does go between the thru-hull and the pump.
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Doug Snell
None needed between head and holding tank?
You are a great source for clearing my confusion. What prevents backflow between a holding tank and the head? My holding tank will be higher than the exit of my head when the level becomes half or more. Is there a valve in the bottom of the head that stops this flow?
You are a great source for clearing my confusion. What prevents backflow between a holding tank and the head? My holding tank will be higher than the exit of my head when the level becomes half or more. Is there a valve in the bottom of the head that stops this flow?
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Peggie Hall/HeadMistress
Two ways to prevent it
Ideally, the way to prevent backflow from the tank to the toilet and spills out the vent when the boat is heeled is to spec inlet and vent fittings toward the centerline of the boat, away from the hull. When the inlet and vent fittings on the tank are toward the centerline of the boat, tank contents can't flow back toward the head or out the vent when the boat is heeled...because when heeled to one side, waste runs away from the inlet...when heeled to the other side, the vent and head discharge hoses run uphill from the tank. When the inlet fitting is toward the hull, a VENTED loop in the head discharge isn't needed, only a loop/arch in the hose that becomes a "hill" higher than waste can climb over at any angle of heel. However, it's often simpler to just install a vented loop immediately after the toilet. Unfortunately, when the tank vent fitting is toward the hull, there's not much that can be done to prevent waste from overflowing out the vent when heeled on toward the vent thru-hull.
Ideally, the way to prevent backflow from the tank to the toilet and spills out the vent when the boat is heeled is to spec inlet and vent fittings toward the centerline of the boat, away from the hull. When the inlet and vent fittings on the tank are toward the centerline of the boat, tank contents can't flow back toward the head or out the vent when the boat is heeled...because when heeled to one side, waste runs away from the inlet...when heeled to the other side, the vent and head discharge hoses run uphill from the tank. When the inlet fitting is toward the hull, a VENTED loop in the head discharge isn't needed, only a loop/arch in the hose that becomes a "hill" higher than waste can climb over at any angle of heel. However, it's often simpler to just install a vented loop immediately after the toilet. Unfortunately, when the tank vent fitting is toward the hull, there's not much that can be done to prevent waste from overflowing out the vent when heeled on toward the vent thru-hull.
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John Visser
thanks Peggy
You said: Strainers, otoh, have have to be installed up to 12" above the static waterline (waterline while the boat is at rest) to allow the strainer to be removed for cleaning without taking on water... Is that the only reason? On a C36 the strainer can be mounted conveniently near the through-hull/seacock, but not 12" above the waterline; but if I can easily shut the seacock for strainer cleaning, is this O.K.? Thanks, jv
You said: Strainers, otoh, have have to be installed up to 12" above the static waterline (waterline while the boat is at rest) to allow the strainer to be removed for cleaning without taking on water... Is that the only reason? On a C36 the strainer can be mounted conveniently near the through-hull/seacock, but not 12" above the waterline; but if I can easily shut the seacock for strainer cleaning, is this O.K.? Thanks, jv
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Peggie Hall/HeadMistress
I don't know...
I would THINK that as long as the seacock is readily accessible, and you don't forget to close it, it should be ok...but there may be a reason why engine intake strainers shouldn't be below the waterline. It also occurs to me to wonder how failure-prone strainers are...how likely it may be that it could sink your boat if the seacock were left open while the boat is unattended in the slip. Methinks we'd both do a little digging for more info before you install it.
I would THINK that as long as the seacock is readily accessible, and you don't forget to close it, it should be ok...but there may be a reason why engine intake strainers shouldn't be below the waterline. It also occurs to me to wonder how failure-prone strainers are...how likely it may be that it could sink your boat if the seacock were left open while the boat is unattended in the slip. Methinks we'd both do a little digging for more info before you install it.
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John Visser
Yes
I always shut the seacocks if I'm leaving the boat for a day or more, but when we're out cruising the stay open all the time. i got the Forespar sstrainer, which is overkill, (1.5" ports) but seems very rugged. I'm not concerned that it will fail. The only reasonable alternative I can come up with is to mount it under the galley sink, but this too would require several feet of hose.
I always shut the seacocks if I'm leaving the boat for a day or more, but when we're out cruising the stay open all the time. i got the Forespar sstrainer, which is overkill, (1.5" ports) but seems very rugged. I'm not concerned that it will fail. The only reasonable alternative I can come up with is to mount it under the galley sink, but this too would require several feet of hose.
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Doug Snell
Remaining smell removal?
Now that I have successfully installed the system as described (11 hours to the untrained worker), I would like to remove the residual smell that has permiated everything (like the unsealed plywood). Any ideas what would attack this smell and neutralize it? What products have people had luck with?
Now that I have successfully installed the system as described (11 hours to the untrained worker), I would like to remove the residual smell that has permiated everything (like the unsealed plywood). Any ideas what would attack this smell and neutralize it? What products have people had luck with?
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Peggie Hall/HeadMistress
This works
Buy some Raritan K.O. holding tank treatment...it's a live bacteria product that "eats" odor-producing spores (similar products are available at pet supply stores to get rid pet odor accidents, but they’re diluted and considerably more expensive). Clean the spill area with detergent and water, but don't use bleach, Lysol or any other "antibacterial" product. When the area is dry (no more than barely damp), put some K.O. in a trigger sprayer or pump-up garden spray bottle and liberally saturate the area with it. Don't rinse...let it dry, leaving that area open so that plenty of fresh air can circulate for 24 hours. If cushions were affected, clean up and saturate (not dripping wet…just saturate enough to completely penetrate the foam) with K.O., then leave outside in the sunshine to dry all day. That will get rid of the odor permanently. If you still have odor after you’ve closed everything up again, you missed a spot. And by the way, this also works in musty wet lockers. (The above is short excerpt from my book. See link below)
Buy some Raritan K.O. holding tank treatment...it's a live bacteria product that "eats" odor-producing spores (similar products are available at pet supply stores to get rid pet odor accidents, but they’re diluted and considerably more expensive). Clean the spill area with detergent and water, but don't use bleach, Lysol or any other "antibacterial" product. When the area is dry (no more than barely damp), put some K.O. in a trigger sprayer or pump-up garden spray bottle and liberally saturate the area with it. Don't rinse...let it dry, leaving that area open so that plenty of fresh air can circulate for 24 hours. If cushions were affected, clean up and saturate (not dripping wet…just saturate enough to completely penetrate the foam) with K.O., then leave outside in the sunshine to dry all day. That will get rid of the odor permanently. If you still have odor after you’ve closed everything up again, you missed a spot. And by the way, this also works in musty wet lockers. (The above is short excerpt from my book. See link below)
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