Anti-siphon loop above heeled waterline

[stranded]

I am converting our Jabsco Quietflush from fresh to seawater flush. I understand that it mY need an anti-siphon valve above the heeled waterline.

The loo is outboard amidships, so the natural place for the anti-siphon loop is stuck to the topsides. Trouble is, as we do occasionally dip our decks (not for long!), that would mean the loop would have to be above deck level, which is silly.

So the loop is going to have to be below the max heel waterline. The current freshwater intake has a loop with a solenoid about 3ft above the static waterline, which I assume is to stop the loo water siphoning back into the freshwater tanks?

That routing would be the simplest and neatest for the seawater intake as it would avoid having to butcher the furniture, and would be above the normal heeled waterline most of the time. There will be an electric pump between the seacock and the loop.

So my question is, how great is the actual risk of dangerous siphoning in situations where we would anyway want to correct excessive heel as soon as we can, which would presumably break the siphon? Would the presence of the pump reduce the risk? We could of course close the seacock. But this is awkward to access and potentially dangerous for limb, if not life, in conditions where we might need to. So would an easily accessible cut off valve at the top of the loop be seamanlike?

Or do I just suck it up and get my butchery gear out?

 

[Muddy32]

Presumably there is a valve/stop cock on the inlet and outlets. If you are not actively using the head, shut the valves. I only open mine if I need to use the Loo.

 

[stranded]

Presumably there is a valve/stop cock on the inlet and outlets. If you are not actively using the head, shut the valves. I only open mine if I need to use the Loo.

Trouble with that is it’s the head we use at sea and the intake stopcock is in the under sink locker at arms length on the downhill side, so a bit of a stretch and contortion - not something I fancy doing every time we need to use the loo in a big sea - hence the question whether an easily accessible additional valve at the top of the loop would be a a sensible solution. Trouble is, I don’t really understand siphons!

 

[Stemar]

An anti-syphon loop with a vent will still work until the loop goes underwater, and the vent will stop the syphonning as soon as it comes above water level, so it's still a good thing to have.

For the times you're really pushing it, could you put a valve in the pipe in some easily accessible place in the heads?

 

[stranded]

OK, thanks Stemar - I think I can fit both the stop and anti-siphon valves in the existing space, so I’ll plan to do that (and remember to reef a bit sooner!).

 

[Neeves]

Simple answers

I think in big seas the intake and outlet may both be under water longer than you think.

Add a label/notice underlining when the loo has been used, and flushed, close the valve and make the valve simple and obvious. For the neophyte you may need to add instruction on why/how to open the valves.

Ours used to syphon, initially could never understand where all the water came from

Jonathan

 

[Stemar]

Ours used to syphon, initially could never understand where all the water came from

That happened to me once on our Snapdragon. Close-hauled on starboard, and single-handed, pushing things a bit. A bit too much, no, a lot too much for a Snappy, but it was fun. Then I realised there were several inches of water in the cabin. Oops.

 

[webcraft]

Our Vega has a 1" long outlet and no loop on the inlet either but has never syphoned.

Shouldn't the joker valve stop it?

 

[stranded]

Our Vega has a 1" long outlet and no loop on the inlet either but has never syphoned.

Shouldn't the joker valve stop it?

Dunno, but the factory installed plumbing for the seawater fuelled other (manual) head has an enormous great loop at the bow. I’ll install the accessible shutoff valve and anti-siphon loop and hope that the pump and the joker valve might help out if I forget to close the shutoff. TBH we’ve got two automatic bilge pumps which beep loud so the risks of serious harm must be minuscule, but may as well do the best I can.

 

[Forty_Two]

I wouldn't use the Jabsco electric valve for this as it only needs small particles to cause issues with them.

Suggest you use a regular inline manual valve in an easily accessible position.

 

[stranded]

I wouldn't use the Jabsco electric valve for this as it only needs small particles to cause issues with them.

Suggest you use a regular inline manual valve in an easily accessible position.

Thanks - yes - will look at what Tru-design do to match everything else!