Seawater for toilet flush

Bobby P.

Well-known member
Joined
Oct 17, 2018
Messages
440
Fluid Motion Model
C-302 SC
Non-Fluid Motion Model
Boston Whaler
Vessel Name
The Retreat
Why not use seawater for toilet flush?

We are going to do some extensive cruising and want to save our fresh water for drinking, washing and doing dishes.
Don't want to waste fresh water to flush.

My last trawler was totally salt water flush and never had any problems.

I'm thinking of converting. Anyone want to try and save met?

Thanks,
Bobby
 
We considered the same thing when we were planning for our extended cruising in Alaska (four month trip). It’s ironic because the Ranger model that you (and we) have is one of the very few that is supplied by the factory with fresh water flush. Most of the people who want to convert are going the other direction—from salt water to fresh. We thought about converting over and then I figured if I was going to go to that trouble, I should go a little further and make it so we could have the option of either one. Fresh water does keep the head cleaner and fresher smelling. (We also had a previous boat with salt water flush.)

It is certainly a matter of personal preference. If you do convert over, remember to put some “insurance” in the system, like a normally closed solenoid that shuts off the water. If the switch that calls for water gets stuck in the “on” position (or a hose clamp comes loose) and you are using fresh water, all it will do is empty your fresh water tank (water that was was already aboard), it won’t sink the boat. The seawater inlet, if you are using an on-demand pump like the fresh water heads use, has an inexhaustible supply.

In our case, I went so far as to get a back of the envelope drawing from a marine sanitation shop on a suggested configuration. In the end, we kept what we have and are happy we did. I figured we could just keep a small bucket of seawater in the head for manual flushing when we needed to conserve water and that would be a lot less trouble than replumbing. Turns out that we didn’t even feel a need to do that.

When feeling a need to conserve water, we learned to push both buttons above the toilet simultaneously for a flush and then push the left one to put a little water back in the bowl. This does not clean the bowl as well as a full automatic flush but then neither does seawater. Remember too that if you are cruising in the US, your holding tank rather than your water tank may be the limiting factor. Wherever you go for a pumpout you can usually take on fresh water nearby.

John
 
I have used salt water and I don't recommend it at all. Why, remember what salt water really is. It s full of small organic material. When that water stays in the lines for a few hours it will smell. AND it can smell bad!
 
iggy":2opbmn2c said:
I have used salt water and I don't recommend it at all. Why, remember what salt water really is. It s full of small organic material. When that water stays in the lines for a few hours it will smell. AND it can smell bad!

Some vinegar application in the lines solve this 'smell' issue - be sure to fill the input strainer with the vinegar mixture as well and let sit for a while and then flush. I will also now and then pour a cup or two bleach/clorox into the toilet bowl to kill the 'critters'.

On my late R25 (Classic) with its stock manual seawater flushing head, I converted over to use fresh water. It was a tough conversion, having to change out the toilet and plump and wire for the electrics. My cost at the time approached $1,000. Would I do it again? - absolutely not. 😀
 
I’ve had both fresh and salt water and, while there’s a learning curve with salt water, either is fine. Definitely a vinegar wash/soak is part of the salt water maintenance (along with Odorlos). But yeah I don’t think I’d pay for the cost of replumbing either way.
 
All our sailboats had salt water toilets. Seawater and urine make crystals that slowly reduce the circumference of the hose going to the holding tank. We could usually get 4 or 5 years before having to replace the hose to the holding tank. We greatly enjoy having a fresh water flush on our RT to avoid this problem, and the smells that come with using salt water.
 
On my last boat I upgraded the head from a manual to an option flush — let you choose whichever you wanted with a push button on the controls. Very well set up and not significantly more expensive than just the baseline electric upgrade (I think head plus all plumbing was under $1k at CSR in Seattle).

sgeary":1lhddowk said:
All our sailboats had salt water toilets. Seawater and urine make crystals that slowly reduce the circumference of the hose going to the holding tank. We could usually get 4 or 5 years before having to replace the hose to the holding tank. We greatly enjoy having a fresh water flush on our RT to avoid this problem, and the smells that come with using salt water.

If you flood your lines with vinegar it will dissolve the crystals. The same sailboat I mention above was as you described; the surveyor noticed the issue and told me privately about the fix; I got some money off the purchase price for the repair but just used vinegar myself. When the lines were pulled for the head upgrade they were clear.
 
Our previous trawler was plumbed for salt water and we used fresh water from the lavatory instead. Keeps everything fresh smelling and few problems with water use. Also remember yellow let it mellow, brown flush it down to save water.
 
Thanks all for your input.
John, never knew about pushing the two buttons at the same time. Did that on the boat over this weekend and realized how little water is used when you do that. Thank you! Best, Bobby
 
Bobby P.":3cupz0x8 said:
Thanks all for your input.
John, never knew about pushing the two buttons at the same time. Did that on the boat over this weekend and realized how little water is used when you do that. Thank you! Best, Bobby

Bobby, you’re welcome! That’s what I love about this forum, we can all benefit from the collective wisdom and ideas of the entire group.

John
 
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