Converting Jabsco heads from salt water to fresh water flush

[Captain Larry-DH]

I just watched a very good how-to video on this.

I plan to do the same thing as shown in the video, and would appreciate comments from the collective wisdom here. In particular, I'm hoping @Peggie Hall HeadMistress will chime in with her expertise.

The guy who did the video used Jabsco anitsiphon solenoid part number 37038-1012, but this seems to have been discontinued and replaced with a new part # 37038-2012

 

[Peggie Hall HeadMistress]

Although it can be done, "coverting' any sea water toilet to use the boat's fresh water is a bad idea and every toilet mfr specifically recommends against it, not only because of the risk of bacteria contaminating your fresh water (minimal, but not non-existant), but because sea water toilet pumps are designed to PULL water in...All toilets that are designed to use fresh water must use PRESSURIZED flush water, so the fresh water pump has to be on to flush the toilet (turning it on and off is major PITA because it has to prime each time). The solenoid valve acts like a faucet--opens to allow the water pump to PUSH water into the toilet, closes to turn it off (and fwiw, Jabsco solenoid valves only have an average 2-3 year lifespan) which can mess up o-rings etc in the toilet pump.

All toilets designed to use fresh water also have built in siphon breaks and backflow preventers, so just tapping into the cold water line to the sink and inserting a solenoid valve--even one with a built in vented loop--isn't enough to protect the fresh water supply.

There's a much easier--and very inexpensive--way to "convert" your toilet to use fresh water safely that works on any boat on which the head sink and toilet are on the same side of the keel and the sink drain is below the waterline that will even allow you to switch between sea water and fresh at will :

Re-route the toilet intake line to tee or wye it into the sink drain line as close to the seacock as possible because the connection must be below waterline to work.This will allow you to flush normally with sea water. After you’ve closed the sink drain seacock in preparation to close up the boat (you do close all seacocks before leaving the boat to sit??), fill the sink with clean fresh water and flush the toilet. Because the seacock is closed, the toilet will draw the water out of the sink, rinsing the sea water out of the entire system—intake line, pump, channel in the rim of the bowl and the discharge line,(Water poured into the bowl only rinses out the toilet discharge line). If your toilet is electric, be careful not to let it run dry…doing so can burn out the intake impeller. Or you can keep the sink drain seacock closed except when it's needed to drain the sink and flush with fresh water down the sink all the time...your choice.
It may also be necessary to keep the sink plugged except when in use, with a rubber sink plug or by installing a conveniently located shut-off valve in the drain hose. Otherwise the toilet may pull air through the sink when you try to flush, preventing the pump from priming.

--Peggie

 

[WayneH]

Ms Peggy has it right. We only open the sink seacock when brushing our teeth. The rest of the time it is closed for head flushing. This also helps you keep track of how much liquids is going into the holding tank.

 

[Ralph Johnstone]

This is taking @Peggie Hall HeadMistress 's verbal description and putting it into pictures. This is her idea which I put into play.

HOWEVER, after I installed it in my head (ship's head not my head) and got around to finally posting a picture of it, she accused me of converting it into something that would be more appropriate if found in a petroleum refinery. So, maybe it was bit of a carryover from my working days. Ya can't please all the people all the time .

The above is a schematic of the idea of using the sink as the source of flush water. Below is the as built installation :

The purpose of the installation is primarily to flush out the sea water lines and sewage line to keep everything as clean as practical. The most noticeable improvement is to stop that first inrush of decayed sea water organisms when the head is flushed after not being used for a week. It also avoids the problem of having to walk into the salon and trying to convince everyone that the horrendous smell emanating from the head is due to rotten bugs and not you.

As previously stressed, do not connect your flushing water to your potable water. In the above installation, there is an air gap of 6" between the source of potable water (the faucet outlet) and the suction for the flushing pump (the bottom of the sink).

 

[Captain Larry-DH]

Although it can be done, "coverting' any sea water toilet to use the boat's fresh water is a bad idea and every toilet mfr specifically recommends against it, not only because of the risk of bacteria contaminating your fresh water (minimal, but not non-existant), but because sea water toilet pumps are designed to PULL water in...All toilets that are designed to use fresh water must use PRESSURIZED flush water, so the fresh water pump has to be on to flush the toilet (turning it on and off is major PITA because it has to prime each time). The solenoid valve acts like a faucet--opens to allow the water pump to PUSH water into the toilet, closes to turn it off (and fwiw, Jabsco solenoid valves only have an average 2-3 year lifespan) which can mess up o-rings etc in the toilet pump.

All toilets designed to use fresh water also have built in siphon breaks and backflow preventers, so just tapping into the cold water line to the sink and inserting a solenoid valve--even one with a built in vented loop--isn't enough to protect the fresh water supply.

There's a much easier--and very inexpensive--way to "convert" your toilet to use fresh water safely that works on any boat on which the head sink and toilet are on the same side of the keel and the sink drain is below the waterline that will even allow you to switch between sea water and fresh at will :

Re-route the toilet intake line to tee or wye it into the sink drain line as close to the seacock as possible because the connection must be below waterline to work.This will allow you to flush normally with sea water. After you’ve closed the sink drain seacock in preparation to close up the boat (you do close all seacocks before leaving the boat to sit??), fill the sink with clean fresh water and flush the toilet. Because the seacock is closed, the toilet will draw the water out of the sink, rinsing the sea water out of the entire system—intake line, pump, channel in the rim of the bowl and the discharge line,(Water poured into the bowl only rinses out the toilet discharge line). If your toilet is electric, be careful not to let it run dry…doing so can burn out the intake impeller. Or you can keep the sink drain seacock closed except when it's needed to drain the sink and flush with fresh water down the sink all the time...your choice.
It may also be necessary to keep the sink plugged except when in use, with a rubber sink plug or by installing a conveniently located shut-off valve in the drain hose. Otherwise the toilet may pull air through the sink when you try to flush, preventing the pump from priming.

--Peggie

Thanks for weighing in on this, @Peggie Hall HeadMistress. In my case, the sink drains are above waterline, and I have no plans to keep the salt water intake connection or pump. The following question is not intended as a challenge or debate, I’m just trying to become educated.
If I plumbed the system the way the guy did in the video, even if the pressure is turned off on the water system I don’t understand how there could be any backflow from the bowl. How would there be a risk of freshwater system contamination considering the water feeds the toilet bowl at the rim, and the pressurized fresh water would be coming in from the solenoid breaker?

 

[Captain Larry-DH]

@Peggie Hall HeadMistress I found this post on Cruisers Forum, and it appears that you are OK with this concept in post #11 Jabsco Electric Toilet Conversion to Fresh Water - Cruisers & Sailing Forums
I would disconnect the salt water intake and pump from the bowl intake, and it would not be y-valved.

 

[Peggie Hall HeadMistress]

Note that I said, "As long as the water pump remains on, the fresh water supply to the toilet remains pressurized...next to -0- risk." That would require leaving the water pump on all the time, even when away from the boat. There's nothing wrong with doing that...I used to leave mine on to feed the ice maker.

Every toilet mfr warns against connecting a sea water toilet to the fresh water plumbing. While some boat owners are skilled enough at DIY modifications to do what's necessary to reduce the risk of contamination damage or contamination to "next to 0," not all do. I have to tailor my advice to the "lowest common denominator."
So I'm just gonna say, it's your boat...do whatever floats it for you.

--Peggie

 

[Captain Larry-DH]

Every toilet mfr warns against connecting a sea water toilet to the fresh water plumbing.

Taken out of context of this thread I believe that’s probably true. I suspect in the context of this conversation it’s also the proper lawyer‘s answer.
I received the Jabsco part # 37030-2012. In the Features portion of the product insert it says: “The duel check valve ensures that there is no backflow from the toilet into the water system.” I think this is an acceptable solution for the way I intend to install it (independent from any salt water intake). The supply will solely feed the toilet bowl at the rim.
I had originally planned to install a y-valve and transfer switch to make it quick and easy to switch back to salt water when desired, but due to your influence will leave the the salt water supply and pump completely disconnected. I may do away with them at a later date. (My boat has a 200 gallon fresh water capacity and I’m also planning to use a water maker. The boat also has enough solar and battery power to run it as needed.)
Thanks for your input. I’ll let you know if it doesn’t work out.