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Old 18-01-2021, 07:40   #1
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Making My Heads Salt Water or Fresh Water Flush

My wife and I own a 2019 Lagoon 42, Ocean Song. She is a 3-cabin owners version with three salt water, electric heads. All three heads have commoderizers, in-line chlorine treatment. The commoderizers work great and we have yet to have any foul odors or calcium build up in our hoses.

We are thinking about plumbing the heads so that we have the option of either salt water or fresh water flush. The reason is that in certain areas the raw water can be pretty dirty. Just as there are places we don't run the water maker, there are places I don't want the raw water in our toilet bowls. In some marinas for example we see water we don't want in our toilet bowls and occasionally in an anchorage there can be enough run off after a heavy rain for the water to be quite murky.

We'd like to have the option of going to a fresh water flush temporarily. If the raw water isn't dirty the commoderizers make the salt water flush perfectly fine. We will continue to use salt water as our primary option to conserve fresh water. We are capable of producing our own fresh water, but we still try to conserve when possible.

I would like to solicit ideas about a good setup. On the fresh water side we have seen conversions with solenoid and anti syphon valves, with the solenoid wired in to the electric head's dedicated (salt water) pump. We will likely include check valves as a backup to the all-in-one solenoid and anti-syphon valves as extra protection for our fresh water supply. A conversion from salt to fresh water flush seems relatively straight forward but there are a couple of questions that arise if we want to keep the salt water flush option available. Any advice is welcomed and if my assumptions are wrong, let me know. I also know there's more than one way to do it, but I'm looking for a well-tested way.

The Basics:

1) We would "T" into the ship's fresh water supply under the sink in the head, route the fresh water into and through the solenoid and anti-syphon valve, then into a ball valve.

2) On many conversions with electric heads, the salt water line into the head is simply capped off. The solenoid is wired into the salt water pump so that it's activated when the head is flushed. I assume I can place the ball valve between the pump and head, route the salt water line into the same ball valve mentioned above and that would allow us to switch between fresh water and salt water flush.

3) It seems that we need to keep our thru hull open supplying salt water to the head's electric pump so that it doesn't burn out. Since I've seen installations (on YouTube - Out Chasing Stars) that simply cap off the salt water line, a closed ball valve should work.

4) My hope is that we can design a system, that once installed, with the turn of a couple of valves we can switch between water sources. Although we don't want to waste money, we don't mind spending a couple of hundred dollars per head to make it right. We plan to live aboard for several years.
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Old 18-01-2021, 08:14   #2
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Re: Making My Heads Salt Water or Fresh Water Flush

Jim,

I have done this on a few vessels. The setup is fairly simple with a solenoid and a simple switch. The solenoid is plumbed into the fresh water and teed in between the salt water pump and the head. A switch is installed to toggle power between the salt water pump and the solenoid. When switching from salt to fresh, you would close the thru hull and flip the switch to fresh. When switching from fresh to salt, flip the switch to salt and open the thru hull.
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Old 18-01-2021, 08:18   #3
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Re: Making My Heads Salt Water or Fresh Water Flush

While I can't offer any specific advice on the installation, I suggest researching the ABYC standards and following them. If you ever sell her, it's something the surveyor would be likely to call out. Good luck on the project.
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Old 18-01-2021, 20:48   #4
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Re: Making My Heads Salt Water or Fresh Water Flush

Best not to plumb your salt water head to freshwater system directly unless the head is specifically designed for both (like a Marine Elegance). Safer to Y valve off the sink drain. Fill sink with fresh water, Close sea intake, open Y valve from sink drain, flush head (with fresh H2O from sink). Zero risk of contaminating your fresh water supply
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Old 18-01-2021, 21:05   #5
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Re: Making My Heads Salt Water or Fresh Water Flush

Quote:
Originally Posted by Flatswing View Post
Best not to plumb your salt water head to freshwater system directly unless the head is specifically designed for both (like a Marine Elegance). Safer to Y valve off the sink drain. Fill sink with fresh water, Close sea intake, open Y valve from sink drain, flush head (with fresh H2O from sink). Zero risk of contaminating your fresh water supply
My boat has this system... Iíve never switched to fresh water but itís there. Good luck.
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Old 18-01-2021, 21:16   #6
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Re: Making My Heads Salt Water or Fresh Water Flush

Our Manta catamaran came standard with a y valve for fresh or saltwater head flushes. Basically, its a y valve with one "in" coming from the normal pressurized fresh water system and another "in" that comes from our sea chest. After the y valve it goes into a pump that supplies the anchor washdown and the electric heads.

We use only fresh water for our flushes - no smell in the heads and very little build up of mineral in the hoses.
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Old 18-01-2021, 22:04   #7
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Re: Making My Heads Salt Water or Fresh Water Flush

Why not using a shower head to feel the toilet bowl when needed?
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Old 19-01-2021, 04:13   #8
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Re: Making My Heads Salt Water or Fresh Water Flush

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Originally Posted by Lost Horizons View Post
Why not using a shower head to feel the toilet bowl when needed?
Indeed.
This provides an “air gap” (twixt potable water & sewage), which prevents any contaminants, in the toilet, from flowing into the potable water system, by siphonage, and is the simplest, least expensive form of backflow prevention.
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Old 19-01-2021, 04:41   #9
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Re: Making My Heads Salt Water or Fresh Water Flush

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Why not using a shower head to feel the toilet bowl when needed?
This!!!
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Old 19-01-2021, 10:12   #10
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Re: Making My Heads Salt Water or Fresh Water Flush

For most sailors fresh water is rationed due to limited supplies. I see no odor issues with using abundant salt water so cannot see using fresh water as a good idea.
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Old 19-01-2021, 11:23   #11
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Re: Making My Heads Salt Water or Fresh Water Flush

Quote:
Just as there are places we don't run the water maker, there are places I don't want the raw water in our toilet bowls. In some marinas for example we see water we don't want in our toilet bowls and occasionally in an anchorage there can be enough run off after a heavy rain for the water to be quite murky.
This makes no sense to me. You defecate in your toilet bowls, right? And you don't drink out of them, right? You think water in the occasional anchorage is going to be "dirtier" than what you defecate into your toilet?

The reason you don't run a water maker in contaminated anchorages is because it will harm the membrane, and they are expensive and time consuming to replace.

It's pretty simple to clean a toilet.

This dirty water was caused by runoff from the streets of La Paz, Mexico after a rainstorm in September 2019, which also contains sewage due to the poor sanitation system here. The seawater cleared up after a few days, and it didn't harm our sparkling white Groco toilet one bit.


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Old 19-01-2021, 12:04   #12
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Re: Making My Heads Salt Water or Fresh Water Flush

On our 1985 Catalina 30, the seacock for the raw water intake for the head is shared with the sink drain. If you close the seacock and fill the sink, you are flushing with fresh water and no concern about back flow contaminating your water supply. Open seacock and sink drains overboard and head flushes with seawater.
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Old 19-01-2021, 13:36   #13
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Re: Making My Heads Salt Water or Fresh Water Flush

Go fresh!! Save 1 head for salt and deem it the off shore potty. There’s a lot of life in my local waters, standing salt water has a dirty smell most who have a working nose would liken to a gas station toilet. Also cycling the fresh water on boats is 100% a good thing esp if you have a water maker. IMHO��������*♂️
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Old 19-01-2021, 16:58   #14
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Re: Making My Heads Salt Water or Fresh Water Flush

I rigged a fifty liter tank with a siphon-breaker overflow to the ocean (or greywater tank if you have to have one), and used the water from my freshwater shower sump (with blackwater waste tank sanitizer added through the shower drain). The rest of the blackwater tank sanitizer is added if required through the bowl of the heads. One person's normal freshwater showering keeps the flushing tank tank full, and never a problem with the electric heads. No smell, no lime build-up.

I used a cheap bladder tank, mounted in a locker. The impeller in the heads drew the water up from the tank through a siphon-breaker, with an electric solenoid valve to seal the breaker duckbill pipe, but only while the impeller is working. If you do not use the last complication, the water will pass from the heads back to the tank and vice-versa as the vessel pitches. Of course--the siphon breaker outlets must always be exited well above the heeled water line.

When the bowl is empty of human waste and one takes one's finger off the flush button, the water between the holding tank top inlet and the heads, as well as that amount remaining in the siphon breaker leg on the heads side, runs back into the bowl partially filling it and sealing off any odors from the holding tank piping, or the flushing recycled shower water tank.

One MUST use portable toilet or blackwater holding tank sterilant in the recycled shower water though. If you do not, it will stink somethin' awful.
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Old 19-01-2021, 22:39   #15
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Re: Making My Heads Salt Water or Fresh Water Flush

Ideally a small header tank to supply the freshwater if you have room. I have seen this arrangement optioned on production boats. Keeps the potable water totally separate.
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