I'm replacing the head on our boat (old Jabsco with a new Jabsco). I've got everything in place but I'm waiting on a length of sanitation hose. The old head/system was backing up. I get the impression that is the (pardon the pun) number one issue with marine heads, especially one with some years. From the reading (bought your book and read it - Thank You Peggie Hall) and research I've done I feel like I need a vented loop in the sanitation hose. The old head system did not have a loop in the sanitation hose. When I looked at the old system, it seemed likely to me, on a good heel, the holding tank could backfill the hose. Two things I want to double check here: 1. Should the loop be close to the head or the holding tank. I believe I read the closer to the head the better. I'm at work and my memory fails me. Does it matter that much? 2. While at a small marine store I browsed what I believe to be a vented loop. It didn't look like it was designed to connect a hose for venting overboard. Is a vented loop generally a two way vent or does it just allow air in? Thanks for your input.
Vented loop before connection to holding tank
- Thread starter jkhill
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No vented loop needed between toilet and tank
Vented loops are only needed in lines that connect to a below-waterline thru-hull. A vented loop's purpose is to break a siphon, which is highly unlikely--if not impossible--in the line from the toilet to the tank, 'cuz even if an overfull tank runs back toward the toilet, as soon as the level in the tank drops below the top of the tank inlet fitting the flow ("siphon") is broken. If your tank inlet fitting is to the outboard--as opposed to toward the centerline--side of the boat, even a half full tank can spill into the head discharge line, so a loop--not a vented loop, just a loop--could be advisable (although I'd move the inlet fitting instead if it were my boat). If so, put it as close to the toilet as possible to provide the shortest uphill run from the toilet. And then learn to flush long enough in the dry mode to move bowl contents over the top of it. The backup you've been experiencing is most likely waste left sitting in the line because you haven't been pumping long enough in the dry mode to move it all the way to the tank. However, ou DO need a vented loop in the head intake. It belongs between the pump and the bowl as shown in the toilet installation instructions--NOT between the thru-hull and the pump!--and should be at least 6-8" above waterline at any angle of heel. You looked at what you THOUGHT was a vented loop. Every marine catalog has 'em, so go to the WM or Defender or any other site and find vented loops so you'll KNOW what they look like. They're designed to include an air valve--which is integral to some versions or can be a separate doodad that threads into the hole in the nipple at the top of some versions--that only allows air INTO a line, nothing out.
Vented loops are only needed in lines that connect to a below-waterline thru-hull. A vented loop's purpose is to break a siphon, which is highly unlikely--if not impossible--in the line from the toilet to the tank, 'cuz even if an overfull tank runs back toward the toilet, as soon as the level in the tank drops below the top of the tank inlet fitting the flow ("siphon") is broken. If your tank inlet fitting is to the outboard--as opposed to toward the centerline--side of the boat, even a half full tank can spill into the head discharge line, so a loop--not a vented loop, just a loop--could be advisable (although I'd move the inlet fitting instead if it were my boat). If so, put it as close to the toilet as possible to provide the shortest uphill run from the toilet. And then learn to flush long enough in the dry mode to move bowl contents over the top of it. The backup you've been experiencing is most likely waste left sitting in the line because you haven't been pumping long enough in the dry mode to move it all the way to the tank. However, ou DO need a vented loop in the head intake. It belongs between the pump and the bowl as shown in the toilet installation instructions--NOT between the thru-hull and the pump!--and should be at least 6-8" above waterline at any angle of heel. You looked at what you THOUGHT was a vented loop. Every marine catalog has 'em, so go to the WM or Defender or any other site and find vented loops so you'll KNOW what they look like. They're designed to include an air valve--which is integral to some versions or can be a separate doodad that threads into the hole in the nipple at the top of some versions--that only allows air INTO a line, nothing out.
Thanks
OK so I don't need a vented loop - Good! That will be less to mess with. I'm not sure if I will be able move the tank around, but I'll look into that first. The intake does have a vented loop that seems to be doing its job. Well if my hose is "in" (its been "Going to be in" for coming up on three weeks now), I should operation tomorrow. If it is not in, I'll just order it myself - something I probably should have done to begin with. Thanks again for your help, and great book! There is a lot of useful information there.
OK so I don't need a vented loop - Good! That will be less to mess with. I'm not sure if I will be able move the tank around, but I'll look into that first. The intake does have a vented loop that seems to be doing its job. Well if my hose is "in" (its been "Going to be in" for coming up on three weeks now), I should operation tomorrow. If it is not in, I'll just order it myself - something I probably should have done to begin with. Thanks again for your help, and great book! There is a lot of useful information there.
Vented Loops
Peggie - I've got one of those Jabsco heads that has the electric retro-fit pump. You know the one, real noisy, draws lots of amps. It was on the boat when I bought it, and has never had a vented loop. Now, that's bugged me, because it didn't seem right, and if I leave my head thru hull open, my bowl will take on water to what I assume is the water line. (Well below the top of the bowl, but at least 1/4 of the way up.) Now, according to the Jabsco site, it shouldn't have a vented loop, but they do suggest if the bowl is taking on water to run a longer hose from pump to bowl, above the water line. Can you think of a reason why this SHOULDN'T have a vent? T J
Peggie - I've got one of those Jabsco heads that has the electric retro-fit pump. You know the one, real noisy, draws lots of amps. It was on the boat when I bought it, and has never had a vented loop. Now, that's bugged me, because it didn't seem right, and if I leave my head thru hull open, my bowl will take on water to what I assume is the water line. (Well below the top of the bowl, but at least 1/4 of the way up.) Now, according to the Jabsco site, it shouldn't have a vented loop, but they do suggest if the bowl is taking on water to run a longer hose from pump to bowl, above the water line. Can you think of a reason why this SHOULDN'T have a vent? T J
Jen & TJ...
Jen, you don't have to move the tank, only the inlet fitting, which isn't that hard to do any more, thanks to a li'l gadget called the UniSeal http://www.aussieglobe.com/uniseal1.htm TJ, I dunno who writes Jabsco's instructions, 'cuz I've seen some real head scratches in some of 'em. You're right--you DO needed a vented loop in the intake, plumbed the same way as a manual pump (between the pump and the bowl)...'cuz all toilets, manual and electric, start a siphon going when the pump primes. Without a siphon break, if the toilet--or any part of it--is below the waterline, water will just keep flowing if you leave the toilet in the wet mode and the seacock is open.
Jen, you don't have to move the tank, only the inlet fitting, which isn't that hard to do any more, thanks to a li'l gadget called the UniSeal http://www.aussieglobe.com/uniseal1.htm TJ, I dunno who writes Jabsco's instructions, 'cuz I've seen some real head scratches in some of 'em. You're right--you DO needed a vented loop in the intake, plumbed the same way as a manual pump (between the pump and the bowl)...'cuz all toilets, manual and electric, start a siphon going when the pump primes. Without a siphon break, if the toilet--or any part of it--is below the waterline, water will just keep flowing if you leave the toilet in the wet mode and the seacock is open.
Thanks Peggie
Thanks for confirming that I wasn't losing my mind. I've been keeping the thru hull closed, because I was tired of filling my holding tank with lake water on every flush. Next trip to the boat, vented loop. And I wish this Jabsco would just finally die so that I could justify replacing it and its noisy pump with a nice quiet manual Raritan. T J Furstenau
Thanks for confirming that I wasn't losing my mind. I've been keeping the thru hull closed, because I was tired of filling my holding tank with lake water on every flush. Next trip to the boat, vented loop. And I wish this Jabsco would just finally die so that I could justify replacing it and its noisy pump with a nice quiet manual Raritan. T J Furstenau
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