Fresh water flushing with sea water toilet?

[marchem]

In a recent thread, Peggy said:

"It is true that NO toilet designed to use SEA WATER should ever be connected to the potable water system. However, it IS safe to connect toilets that are DESIGNED BY THE MFR TO USE PRESSURIZED WATER to the potable water system. If that were not true, no toilet mfr would offer toilets designed to to be connected to the potable water system--that would be just asking for lawsuits. That every major mfr does offer toilets designed to be connected to the onboard potable water is proof that it IS safe."

I'm wondering how the manufacturer is able to make a system that is safe, but the end user is unable to?

I've got a Catalina 27 with a fresh water tank we never use. I'd sure like to plumb it to the head (Headmate), but I want to do it right. For now I've added a second valve and a short length of hose that I stick in a bucket of fresh water. Works great, but is a little awkward. No sink in the head, so can't use the sink drain.

 

[Johnb]

Is the issue that when building the flushing system to draw from outside the manufacturer need not worry about accidently contaminating the source, but when designed to use domestic water it is inherently built so that nasty stuff can't get back into the fresh water system.

In a typical seawater flushing system there is not much between the source of flushing water and the outlet other than the seals in the pump and valves.

 

[markwbird]

backflow issues

A head designed to be plumbed into the freshwater system has gizmos that prevent backflow or back siphoning into the freshwater tank. A seawater head does not. Without that you will likely get some contamination of the freshwater and that is bad even if you do not intend to use it for anything else right now. What about installing some type of dedicated tank that feeds only the toilet? One that could never be used for anything else by you or future owners of the boat. It could hold enough for a weekend or so.

 

[Jackdaw]

You need a septic break in the system. It's why your home toilet squirts water into the toilet tank. You cannot have a solid piped connection. Use your sink to make the break.

 

[Sanfelice]

My boat has the water pass through the sink drain and toilet pumps water from the sink through the bowl and into the holding tank. Simple operation. Fill sink with water, flip the lever on head and pump. Switch lever back to dry flush and pump. Simple.

 

[Peggie Hall HeadMistress]

I've got a Catalina 27 with a fresh water tank we never use. I'd sure like to plumb it to the head (Headmate), but I want to do it right.

*IF* there is NO shared plumbing between your potable water system and your unused water tank and toilet intake--and by NO shared plumbing, I mean totally separate deck fill fitting and fill line, hoses and even the the vent line--you can safely convert it to flush water supply for your toilet...because it becomes a separate water supply dedicated to the toilet. But you can never convert it to integrate into your potable water supply without risk.

Fwiw, there are no manual toilets designed to use pressurized flush water, only electric
toilets. It could be done, but it's just not practical. The only solutions are a connectiion to a sink drain line or--what you want to do--a separate flush water tank.

 

[marchem]

You need a septic break in the system. It's why your home toilet squirts water into the toilet tank. You cannot have a solid piped connection. Use your sink to make the break.

If I had a sink in there I would do that.

 

[marchem]

A head designed to be plumbed into the freshwater system has gizmos that prevent backflow or back siphoning into the freshwater tank. A seawater head does not. Without that you will likely get some contamination of the freshwater and that is bad even if you do not intend to use it for anything else right now. What about installing some type of dedicated tank that feeds only the toilet? One that could never be used for anything else by you or future owners of the boat. It could hold enough for a weekend or so.

Why can't I install the same gizmos to prevent back flow?

Adding another tank is not easy because of space and weight, but I'll think more about that.

 

[marchem]

*IF* there is NO shared plumbing between your potable water system and your unused water tank and toilet intake--and by NO shared plumbing, I mean totally separate deck fill fitting and fill line, hoses and even the the vent line--you can safely convert it to flush water supply for your toilet...because it becomes a separate water supply dedicated to the toilet. But you can never convert it to integrate into your potable water supply without risk.

Fwiw, there are no manual toilets designed to use pressurized flush water, only electric
toilets. It could be done, but it's just not practical. The only solutions are a connectiion to a sink drain line or--what you want to do--a separate flush water tank.

There is only one tank now, so I would have to add a new one for this. Space and weight will be issues. Installing a sink might be easier.

Do the electric toilets with pressurized water have a vacuum break, similar to a home toilet? If they only have check valves then why not use the same valves with a manual system?

 

[woodster]

i think that the idea of having the head water isolated from the fresh water supply is to keep the bacteria and all the unhealthy gremlins form having a way to get to your fresh water supply ....as for back flow valves they can malfunction and when they do you have just lost all you fresh water for cooking and bathing...look at it this way would you drop a drinking water bottle full of water in the the unflushed bowl and then just rinse it off and then open the bottle and have a drink of water.....i wouldn't .....the rehab if you are still alive would be very pianful....not to mention the liability to your guest as well .....better safe and healthy than sorry......

regards

woody

 

[Squidd]

I think the break is for bacteria working their way back to the water source... not so much for water "back flow" (which a check valve would prevent) but actual actual contact and surfaces for bacteria to live on and work their way back to tank...

(woodster posted while I was typing this)

 

[woodster]

I think the break is for bacteria working their way back to the water source... not so much for water "back flow" (which a check valve would prevent) but actual actual contact and surfaces for bacteria to live on and work their way back to tank...

(woodster posted while I was typing this)

thats OK by me........ now we have a a woolly version and a velvet version

regards

woody

 

[Peggie Hall HeadMistress]

Do the electric toilets with pressurized water have a vacuum break, similar to a home toilet?

Marine toilets designed to use pressurized flush water have quite a bit more built into them than household toilets. Fresh water plumbing isn't connected directly to the bowl of a household toilet, it's connected to a separate tank that dumps the water into the bowl when the flush lever lifts a plug in the bottom of the tank called a "flapper valve." There is no vacuum break because none is needed.

Marine toilet bowls, otoh, are connected directly to the flush water plumbing...which, which for most toilets that use pressurized flush water would be a cold water line coming off the potable water plumbing. So it's vital to make sure that neither actual bowl contents or bacteria can migrate from the bowl into the potable water supply, even when the water pump is not on to keep the fresh water system pressurized. That requires vacuum breakers, anti-siphon devices AND backflow preventers (check valves) that are a bit different from those in manual toilets.

If they only have check valves then why not use the same valves with a manual system?

As you now know, they don't. Check valves alone wouldn't do the job.

Health concerns are not the only reason why no toilet designed to use raw water (sea water, lake or river water) should ever be connected to the fresh water supply: raw water toilet pumps are designed to PULL water through them...pressurized flush water is PUSHED through the pump, which is likely to mess up the alignment of the seals, valves and o-rings in the toilet.

I'll just betcha that if you really worked at it a bit, you could find a space for 3-5 gallon flush water tank that you could fill with a hose or a bucket...or...you could REALLY simplify your life by pulling the whole system--toilet, holding tank and all the plumbing out and replacing it with a tidy li'l self-contained system. Check out the Thetford Porta Potti 550P MSD The "MSD" designation means it's fitted for pumpout--so no carrying anything off the boat--so is designed to permanently installed. It holds 50-60 flushes--more than twice what I'm guessing your current tank holds...and has no moving parts so you have no toilet maintenance. There's been quite a bit of discussion of "MSD" portapotties here that you can find if you search. Once you give this idea a little thought, I suspect you might decide you like it.

And btw, as long as I have the floor...if your tank vents through a rail stanchion, get it out of there and onto a real thru-hull so the tank--your current tank OR self-contained system tank (both have to be vented)--can BREATHE! A lot of conversation from Catalina owners on here who know the value of THAT little modification too!