Holding tank flushing

[ICENI]

I recently installed a 60 litre holding tank in my Bavaria 32.   I thought long and hard about where to locate it and opted for where other owners have placed theirs - in the lazarette on the aft face of the bulkhead between the aft heads/hanging locker and the lazarette.

When doing so I was aware that the output pipe from the toilet was both long and pretty well vertical.   This would cause quite a bit of the waste filtering back into the toilet bowl!!!   I was quite correct; although I fitted a complete Jabsco toilet kit and more importantly a nice new Joker valve, what I thought would happen in fact, has!   One has to flush four of five times to obtain pleasant clear water in the loo bowl ready for the next user!

The 60 litre tank capacity is therefore considerably reduced which is a real nuisance.

I have emailed the tank manufacturers Messrs Tek Tanks and they said all I could do would be to convert the toilet to electric.

I would be very grateful for any comments on the installation and it's problems please?

One more of my many posts!

[Yngmar]

When did you last service your pump? Most "dirty" flushing water is the result of blow-by on the o-ring around the piston. This is reduced by pumping slower (which reduces pressure) and by servicing the pump, at minimum with a new o-ring to improve the seal around the piston.

The joker valve only serves to stop any backflow from the tank. It normally does this reliably, but only if "clear" of any debris. You can tell if your problem is from backflow if liquid keeps entering the bowl after the flushing lever is put over to the right and the pump stopped.

You can also fit a diverter valve near the toilet, with an input from the toilet output, one outlet to the tank and one direct to a seacock. Now once you're done flushing, set the diverter valve to sea again. This stops any backflow from the tank completely, as that leg is now closed. Could even fit a normal ball valve if you do not want the direct overboard function.

[Symphony]

I assume your inlet into the tank is at the top, or at least in through the bottom then an internal stack pipe. Your problem is that you are simply not pumping enough water through so you still have foul water in the pipe. I pump a minimum of 10 pumps of clean water after the bowl has been cleared. Inevitably that reduces the number of times you can use the toilet within the capacity of the tank.

[Rampage]

Part of the problem is not doing enough “air pumping” after use.  Jabsco state that you need to do 7 pumps per metre of pipe to blow the pipe through after use, so if you’ve got say 4 metres of pipe between the head and the tank, you need to do 30 or so pumps to push all the dirty water into the tank: that’s after the bowl has emptied. 
The other thing to consider is a diverter valve somewhere in the system so that you only use the tank for holding solids: pee can be pumped straight out to sea.  That’s the system we have: a 40l tank does us for about 5 days normal usage.

[Fenders]

I agree with Rampage and Symphony.
On our B32 our holding tank is also aft of the wet locker in the lazarette. We always pump 8 times to be sure that all waste reaches the tank and the bowl has clean water.
When surveyed prior to purchase we were advised that an anti syphon device should be installed  on the sea water inlet. This was also required by our insurers. Simple job.

[Moodymike]

Can you describe how you installed the anti siphon valve? I also have a B32 with holding tank.

[Symphony]

You don't need an anti syphon valve on the inlet as the bowl is above the waterline. The standard Bavaria arrangement does not suffer from syphoning of seawater. If the bowl is below the waterline then an anti syphon valve should be fitted between the pump and the bowl at the top of a loop that goes above the waterline. It is all explained in the Jabsco installation instructions.

In the outlet, the holding tank is effectively an anti syphon valve through the vent. The OP's problem is fluid leaking back under gravity from the outlet pipe into the bowl, and that is what the joker valve is intended to stop. It is less of a problem (from the hygiene point of view) if enough water is pumped through such that only clean water is left in the pipe.

[Keweetoo]

We have the same set up and have found it takes a minimum of 15 full slow pumps to clear the pipe to the holding tank so only clean water is in the pipe. A very small amount of 'foul' water will discolour the water in the bowl if the pipe is not cleared fully.

[Symphony]

When I leave the boat, I empty the tank (at sea) then use the shower to rinse the bowl and pump enough fresh water through to clear the pipe. I leave the seacock open. This reduces the chances of deposits forming in the tank and the outlet hose.

[Fenders]

Moody Mike

The anti syphon valve we fitted cost about £10. Very simple device and easy to fit. I say easy to fit but in fact it was a bit of a pig only because where the seawater inlet hose runs from the sea cock behind the sink to the toilet, space to work is extremely tight when trying to squeeze both arms/hands in  through the under sink cupboard door.
As Symphony correctly says, the valve shouldn’t be needed, however, it had been mentioned by our surveyor and also our insurers. Prior to purchase we were unfamiliar with the boat so any advice offered we were very appreciative and undertook the recommendations received.

[Symphony]

Sorry, but that is the wrong place to put an anitsyphon valve. There is absolutely no need for one - indeed the opposite is sometimes needed, that is a non return valve to ensure the pipe is always full from the seacock to loo pump as it can be difficult to prime the pump on some installations. Are you sure it is not a non return valve? as if it is an antisyphon you could get air into the pipe which is the last thing you want. Go back to your surveyor and ask him why he thinks anything additional is needed. The installation instructions from Jabsco are quite clear. The insurance company has no idea  - it just follows the surveyor's "recommendation"

[Fenders]

Symphony

My mistake. I have checked my paperwork at home as I haven't been down to the boat for a while. It is a non return valve. Apologies for the confusion.
I agree with you that the insurance company are only going by what they read in the survey and are minimising their risk.
Never had any problems before or after installation. On this boat and previous ones I have always pumped 6 - 10 times .

[Symphony]

OK. A NRV is really only needed when the inlet seacock is close to the waterline and could be above when the boat heels, leading to the possibility of water flowing out of the pipe making priming difficult. Although the Bavaria is not very deep, angles of heel are relatively low so the intake does not seem to come out of the water. Perhaps your surveyor was brought up on old style boats which often do heel and expose intakes, both loo  and on some installations I have seen, including on an old boat I owned, the engine coolant intake. When I re-engined that boat I moved the intake lower in the hull and had no further problems.