Jabsco heads plumbing quick question..

[jerrytug]

Hello I am replacing an old SL400 heads with a manual Jabsco,does the discharge pipe need to go in a big loop above the waterline? Or can it go by the shortest route?
Question 2.. Does the pipe from the hand pump to the bowl need to go in a big loop above the waterline and what is the name of the anti- siphon gadget ...if I need one?

As you can guess,the heads is low in the boat,and I want to get the installation right first time to avoid any possible worry about it sinking me!
Thanks for any helpful suggestion cheers Jerry. (Boat is a Hurley 24 going back in the water next week.)

 

[pvb]

It depends whether the toilet is above or below the heeled waterline. The Jabsco instructions are comprehensive, and have diagrams showing what you need. If you follow the instructions diligently, you'll have no problems.

 

[prv]

Both need to loop as high as possible, both need anti-siphons. Otherwise you have a pipe from the sea straight into your boat, protected only by the valves in the toilet pump. If you've ever dismantled one of these pumps and seen the piddling bits of rubber that form said valves, you will agree with the manufacturers that they are not sufficient to keep a boat afloat.

Pete

 

[laika]

As the others have said, yes to both if, as you say, the heads may be below the waterline. Nobody would argue with the discharge side but there may be some disagreement about the pipe from the pump to the bowl. I fitted new jabsco twist 'n' locks in my boat when I bought it. The freshwater vacuflush toilets I replaced were not original, and the holes in the woodwork suggested that the original manual toilets never had a loop between pump and bowl. A couple of people advised me that the new jabsco pump locks were secure enough not to require that loop as the instructions demanded. I asked the jabsco folks at southampton boat show if this was just covering themselves but they assured me that no it was a necessary safety feature. So I started looking on new boats. None of the AWBs with manual jabscos I saw at shows had anything more than a short pipe between the pump and bowl. The only manual jabsco I saw plumbed in "properly" was on a Najad (the other fancy boats all had electric bogs).

I drilled another 2 holes per toilet and ran the required pipework. Not as neat but at least I don't worry about it.

What you're looking for is a "vented loop". See here.

Probably 38mm for the discharge, 19mm for the one between pump and bowl. You don't want to put one between inlet and pump.

 

[Hoolie]

... ... ...
Probably 38mm for the discharge, 19mm for the one between pump and bowl. You don't want to put one between inlet and pump.

On our boat it's not possible to put an anti-syphon between pump and bowl, so I fitted a brass non-return valve (bought at the local plumbers merchant) between the sea cock and the pump inlet.
Works fine - and even with the hose fittings cost less than half a Jabsco 19mm anti-syphon fitting

 

[alahol2]

On our boat it's not possible to put an anti-syphon between pump and bowl, so I fitted a brass non-return valve (bought at the local plumbers merchant) between the sea cock and the pump inlet.
Works fine - and even with the hose fittings cost less than half a Jabsco 19mm anti-syphon fitting

A non-return valve won't prevent it syphoning, it might even encourage it.

 

[pvb]

A non-return valve won't prevent it syphoning, it might even encourage it.

Well spotted!

 

[prv]

On our boat it's not possible to put an anti-syphon between pump and bowl

Why not?

so I fitted a brass non-return valve (bought at the local plumbers merchant) between the sea cock and the pump inlet.

To stop the toilet water jumping up to the holes round the rim and flowing into the sea?

Cos if you fitted it the right way round to still allow flushing, it sure as hell won't stop the sea flowing into the toilet. And then, once the toilet is full, into your boat. How on earth did you expect it to work?

Pete

 

[KellysEye]

>Both need to loop as high as possible, both need anti-siphons.

Our toilet is below the waterline and we have a large loop and no anti-syphon. It's been like that for 20years+ with no problems. I suspect it's so high there is no chance that water can be pushed high enough from the inlet to reach the toilet.

 

[VicS]

>Both need to loop as high as possible, both need anti-siphons.

Our toilet is below the waterline and we have a large loop and no anti-syphon. It's been like that for 20years+ with no problems. I suspect it's so high there is no chance that water can be pushed high enough from the inlet to reach the toilet.

The trouble is that once the loop has been filled with water by the flushing action the water can continue to syphon in if the toilet is below the water line until the seacock is closed unless there is a vent that will allow air to enter and break the syphon.