Switchable fresh water flush for heads.

[Frogmogman]

I’d quite like adapt the heads on my Sun Odyssey 349QR (the one with the hydraulic lifting keel) to flush with fresh water, whilst retaining the ability to switch over to flushing using raw sea water when necessary. FWIW, the boat is to all intents and purposes the boat is brand new, and to the best of my knowledge, the heads have never been used.

The boat is berthed at Saint Quay Portrieux, and the programme envisaged is mainly pottering around the bay of Saint Brieux, Île Brehat, Channel Islands etc, with a couple of longer cruises annually further afield in Brittany, Ireland and the West Country.

The attractions of the fresh water flush are avoiding smelly heads and the ability to flush (into the holding tank) when drying out (one of the big attraction of this model for me for the cruising area envisaged is the ability to easily take the ground with beaching legs on and keel up). It would nonetheless be useful to be able to switch over to raw sea water flush when further from home and marinas, when water economy becomes an issue.

The foot operated pump at the galley sink can be switched between fresh water and sea water by turning a cock under the floor. I guess a similar arrangement for the heads, with a similar cock drawing either raw sea water or fresh water from the tank, (with a non return valve) ought to work.

Any of you guys done this ? Is there anything I’m missing ?

 

[Mistroma]

Did it on my Jeanneau 42DS in forward head. Just a T-piece in flush hose and another in basin outlet hose. Connecting hose with a valve.

It works well by simply filling basin with outlet valve off to provide flush water. I only fresh flush every few weeks and leave the hose full of fresh till next use. The connecting valve is normally closed and sea-water flush just operates in usual manner.

It certainly works to control odour when flushing. Very cheap modification with no chance of contamination with no link to water tank and easy to install. Another advantage is ease of adding disinfectant or other agent if you do get bacterial growth in the flush pipe.

 

[jac]

Did it on my Jeanneau 42DS in forward head. Just a T-piece in flush hose and another in basin outlet hose. Connecting hose with a valve.

It works well by simply filling basin with outlet valve off to provide flush water. I only fresh flush every few weeks and leave the hose full of fresh till next use. The connecting valve is normally closed and sea-water flush just operates in usual manner.

It certainly works to control odour when flushing. Very cheap modification with no chance of contamination with no link to water tank and easy to install. Another advantage is ease of adding disinfectant or other agent if you do get bacterial growth in the flush pipe.

I had to think that though in my head but can I say sir - that is a piece of genius!!!!

 

[ithet]

We occasionally flush the heads and holding tank using the shower head which reaches from the basin on our Beneteau.

 

[Clancy Moped]

On our SO 37 we used the shower hose.

 

[Mistroma]

Using the shower doesn't treat bugs in the inlet pipe. It only flushes the bowl and outlet pipes. Anaerobic bacteria in the inlet hose are the source of the rotten egg smell.

It does address one of OP's needs.

 

[Mistroma]

I had to think that though in my head but can I say sir - that is a piece of genius!!!!

Thanks for the compliment.

Not so much genius, more stinginess. I'm Scottish and had just replaced a valve. The old one was in good condition. Seemed a shame not to use it. No risk if it failed as it is above the waterline.

 

[Birdseye]

I’d quite like adapt the heads on my Sun Odyssey 349QR (the one with the hydraulic lifting keel) to flush with fresh water, whilst retaining the ability to switch over to flushing using raw sea water when necessary. FWIW, the boat is to all intents and purposes the boat is brand new, and to the best of my knowledge, the heads have never been used.

The boat is berthed at Saint Quay Portrieux, and the programme envisaged is mainly pottering around the bay of Saint Brieux, Île Brehat, Channel Islands etc, with a couple of longer cruises annually further afield in Brittany, Ireland and the West Country.

The attractions of the fresh water flush are avoiding smelly heads and the ability to flush (into the holding tank) when drying out (one of the big attraction of this model for me for the cruising area envisaged is the ability to easily take the ground with beaching legs on and keel up). It would nonetheless be useful to be able to switch over to raw sea water flush when further from home and marinas, when water economy becomes an issue.

The foot operated pump at the galley sink can be switched between fresh water and sea water by turning a cock under the floor. I guess a similar arrangement for the heads, with a similar cock drawing either raw sea water or fresh water from the tank, (with a non return valve) ought to work.

Any of you guys done this ? Is there anything I’m missing ?

Mistromas idea seems very sound to me . I hate the idea of a non return valev seperating the toilet contents from the drinking water. Non return valves regularly fail.

 

[Clancy Moped]

Using the shower doesn't treat bugs in the inlet pipe. It only flushes the bowl and outlet pipes. Anaerobic bacteria in the inlet hose are the source of the rotten egg smell.

It does address one of OP's needs.

The inlet pipe seacock was closed.

 

[Mistroma]

The inlet pipe seacock was closed.

My point exactly, no movement of water through the hose from the inlet skin-fitting to the bowl. Subsequent normal flushes will move some of the gas generated by bacteria into the boat. The only part being fresh water flushed is downstream of the bowl and being expelled from the boat anyway.

Fine if you only use the shower to flush and never use the normal route at all.

 

[Clancy Moped]

My point exactly, no movement of water through the hose from the inlet skin-fitting to the bowl. Subsequent normal flushes will move some of the gas generated by bacteria into the boat. The only part being fresh water flushed is downstream of the bowl and being expelled from the boat anyway.

Fine if you only use the shower to flush and never use the normal route at all.

The inlet pipe was empty of any water with the seacock closed, so no bugs and no smells.

 

[Mistroma]

The inlet pipe was empty of any water with the seacock closed, so no bugs and no smells.

That will work. You never use the seawater flush and keep the hull inlet valve closed pre-launch for the whole season in order to keep it filled with air. I had not realised that was the case, pretty unusual. Most people open the valve at some point and use seawater at least some of the time.

 

[ibbo]

I have a Lavac vacuum toilet for the first time, after years of Jabsco smelliness.

It would be an interesting test to pump seawater in to flush the toilet via a seperate pump, rather than the combined one. The Lavac flushes with sea water, and never smells when left.

I think the smell must come from some mixing of the out water with the in, which can't be good. If it was plain sea water then I expect the Lavac would smell like all the others.

 

[Frogmogman]

Mistromas idea seems very sound to me . I hate the idea of a non return valev seperating the toilet contents from the drinking water. Non return valves regularly fail.

My concern about the idea is all to do with possible contamination.

Mind you, as the freshwater would be tapped into the inlet pipe just above the seacock, on the supply side of the loo rather than waste side, I don’t see why it would be any more problematic than any fresh water flush system from this point of view. I suppose there would be a risk of siphon effect from the seacock into the freshwater tank.

I guess the alternative would be to add a small additional propylene freshwater tank - Maybe 30 or 40 L just to supply the water for flushing.

In any case, I’ve asked the excellent local yard, Cras Nautique, (who have already done quite a few bits and bobs for me ) what they reckon.

 

[Moodysailor]

Teeing into the basin outlet as mentioned above is one of the simplest and most effective ways. There is a risk (however small, still a risk) that if tee'd into the FW line a failure on the pump could cause effluent to contaminate the water on board.

Most FW kits that are designed for using the pressurised water use a solenoid valve and back-flush preventer valve, but eliminate the sea water pump so it would take some elaborate and unnecessarily complicated plumbing to combine sea water and pressurised FW flush with the right valves to prevent any risk of contamination. A simple tee into the sink outlet uses all the existing hardware and meets the K.I.S.S test.

 

[jac]

Teeing into the basin outlet as mentioned above is one of the simplest and most effective ways. There is a risk (however small, still a risk) that if tee'd into the FW line a failure on the pump could cause effluent to contaminate the water on board.

Most FW kits that are designed for using the pressurised water use a solenoid valve and back-flush preventer valve, but eliminate the sea water pump so it would take some elaborate and unnecessarily complicated plumbing to combine sea water and pressurised FW flush with the right valves to prevent any risk of contamination. A simple tee into the sink outlet uses all the existing hardware and meets the K.I.S.S test.

Indeed - I can't see any way that the tee into a sink outlet could ever cause contamination. Not a solution for permanent FW flushing but i would argue that that is not really needed. Just a FW flush before leaving the boat ( or if dried out) should suffice for most people!

 

[Moodysailor]

Indeed - I can't see any way that the tee into a sink outlet could ever cause contamination. Not a solution for permanent FW flushing but i would argue that that is not really needed. Just a FW flush before leaving the boat ( or if dried out) should suffice for most people!

With the added benefit that you can flush with warm water for cleaning

There is zero chance of cross-contamination with this setup as the fresh water tank/line is not connect directly to the heads.

 

[Frogmogman]

With the added benefit that you can flush with warm water for cleaning

There is zero chance of cross-contamination with this setup as the fresh water tank/line is not connect directly to the heads.

It does have an elegant simplicity to it as an idea. And as you say zero chance of getting unpleasant backwash…

One could also add a cupful of cleaning product into the sink from time to time when flushing is on progress.

 

[mjcoon]

One could also add a cupful of cleaning product into the sink from time to time when flushing is on progress.

As said in post #2...

 

[Poecheng]

I had to think that though in my head but can I say sir - that is a piece of genius!!!!

Ha, nice work !