Jabsco Vent Valve (anti-syphon)

[Jaguar 25]

I need to sort out the discharge and supply pipes to my Jabsco marine loo to make sure the loop is higher than sea level plus a bit. Currently they rest against the inside of the hull without being fixed in any way.

Is it worth fitting the anti-syphon vent valves at the same time?

 

[VicS]

I need to sort out the discharge and supply pipes to my Jabsco marine loo to make sure the loop is higher than sea level plus a bit. Currently they rest against the inside of the hull without being fixed in any way.

Is it worth fitting the anti-syphon vent valves at the same time?

There is not lot of point in having the loops unless the antisyphon vales are fitted in them. They will just siphon!

Note that the vented loop in the inlet pipe replaces the short connection between the pump and the bowl supplied with the toilet. If you put the vent in the pipe between seacock and pump it will suck in air when you try to flush.

 

[vyv_cox]

If your toilet is below sea level, including when heeled, there is a case for an anti-siphon valve. Otherwise it is not possible for the sea below the toilet to siphon into it.

 

[VicS]

There is not lot of point in having the loops unless the antisyphon vales are fitted in them. They will just siphon!

Note that the vented loop in the inlet pipe replaces the short connection between the pump and the bowl supplied with the toilet. If you put the vent in the pipe between seacock and pump it will suck in air when you try to flush.

Although a "twist and lock" pump combined with the joker valve all but eliminates the need for the vented loop on the outlet.

 

[Hoolie]

I can't fit an anti-syphon loop between the pump and bowl so I've fitted a non-return valve (local heating supplies) between the sea-cock and pump. Works well and completely stops siphoning if the heads valve is inadvertently left in the wet position.

 

[VicS]

I can't fit an anti-syphon loop between the pump and bowl so I've fitted a non-return valve (local heating supplies) between the sea-cock and pump. Works well and completely stops siphoning if the heads valve is inadvertently left in the wet position.

But you are not utilizing its non return feature, just relying on a light spring pressure or the weight of a flap to hold it closed

 

[vyv_cox]

But you are not utilizing its non return feature, just relying on a light spring pressure or the weight of a flap to hold it closed

Can be enough though. The head of water in a toilet siphon is only going to be a few inches. I use a NRV in my central heating system to prevent convective heating in the radiators when only heating the hot water tank. Radiator supply is pumped but hot water is not.

 

[VicS]

Can be enough though. The head of water in a toilet siphon is only going to be a few inches. I use a NRV in my central heating system to prevent convective heating in the radiators when only heating the hot water tank. Radiator supply is pumped but hot water is not.

Do they come with different spring pressure ratings. I had a very quick look but found no figures. Obviously on the CH system you want a fairly low pressure but one rated a bit higher might be as well on the toilet ...... no so high that you could not suck water in of course.

 

[Hoolie]

But you are not utilizing its non return feature, just relying on a light spring pressure or the weight of a flap to hold it closed

Yes indeed. It needs quite a "poke" (a technical term) to depress the spring (it's the spring type NOT a flap) and as vyv_cox says it's quite enough to keep the couple of inches of water pressure from syphoning.

I bought mine at the local hardware store and together with the connectors bought at a chandlery the total cost was less than half that of a Jabsco anti-syphon valve!