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Old 06-09-2011, 20:11   #1
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Freshwater-Flush Plumbing

Would like to use on board fresh water to flush with a manual Jabsco unit. Can I plumb from after the pressure pump? Or must it be before?
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Old 06-09-2011, 20:21   #2
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Re: Fresh water flush plumbing

Yuk. Somebody better reply with the requirements for separating the toilet water from the domestic water supply. I wouldn't even try this. Home toilets go to great lengths to prevent backflow. Like two large air gaps and a backflow valve. Marine toilets don't consider this in any way.

Why bother? Make the inlet seawater hose as short as possible. Use the head every day. Devise a way to easily pickle the intake with vinegar when left unused.
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Old 06-09-2011, 20:47   #3
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Re: Fresh water flush plumbing

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Would like to use on board fresh water to flush with a manual Jabsco unit. Can I plumb from after the pressure pump? Or must it be before?

I do it very simply -- a bucket of fresh water in the head. I just flush the head manually, no big deal. I can't stand the smell of the combination of urine and salt water.
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Old 06-09-2011, 21:29   #4
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Re: Freshwater Flush Plumbing

Only safe way is to put a atmospheric vacuum breaker in the fresh water line to the head. Using a N.C. solenoid with a push button and a vacuum breaker mounted 12-18" above the rim hooked up to your fresh water system. I would plum it in with a tee between the pump and bowl connection.

Never ever connect a fresh water line directly to a marine head without some form of backflow prevention. A check valve in the line is not going to do it.
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Old 06-09-2011, 21:48   #5
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Re: Freshwater Flush Plumbing

Replace the existing head with a vacuflush, Mansfield, Dometic, Sealand, etc. These are fresh water flush and use very little fresh water. No check valves or vacuum breaks required. You will never go back to a pump type. The fresh water is connected to the proper input from your pressurized water system.
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Old 06-09-2011, 21:53   #6
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Re: Freshwater Flush Plumbing

This subject has been talked about a lot on this forum. There are ways to do it but generally it's really just a bad idea. If you want a fresh water flush, buy a toilet designed for it. Both Jabsco and Raritan make toilets designed to flush with your pressurized water system.
37045 Series Quiet Flush Electric Toilet - Freshwater > ITT Flow Control - Engineered for life.
http://www.raritaneng.com/pdf_files/...e_seafresh.pdf
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Old 06-09-2011, 22:17   #7
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Re: Freshwater Flush Plumbing

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Would like to use on board fresh water to flush with a manual Jabsco unit. Can I plumb from after the pressure pump? Or must it be before?
Neither...there is no safe way to connect ANY manual toilet to the fresh water plumbing, with or without any vacuum breaker or other bits. However, there IS an alternative that works on most boats...one that most people like:

Reroute the head intake line to tee it into the head sink drain line just ahead of the seacock. This will provide a safe source of clean fresh water to rinse the sea water out of the system before it sits and stagnates...just close the thru-hull, fill the sink with clean water (NOT gray water!)...flush the toilet. Because the seacock is closed, the toilet will pull the water out of the sink, rinsing out the WHOLE system--intake line, pump, channel in the rim of the bowl AND the head discharge line. You CAN keep the seacock closed (except when using the sink) and use this method to flush with fresh water all the time, but most people don't find it necessary. When flushing with sea water, it may be necessary to put a plug in the sink to allow the pump to prime instead of pulling air in air.
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Old 06-09-2011, 22:44   #8
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Re: Freshwater-Flush Plumbing

I have a dedicated "flush water tank" not connected to my fresh water supply, that I manually fill by hose with fresh water from my tanks or the dock.
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Old 07-09-2011, 06:34   #9
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Re: Freshwater-Flush Plumbing

Greetings and welcome aboard the CF, magicboat.
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Old 07-09-2011, 16:12   #10
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Re: Freshwater-Flush Plumbing

All the electric flush toilets that use a fresh water fills that I've seen, all use atmospheric vacuum breakers to protect the fresh water system..

Placing the Atmospheric vacuum breaker 18" or higher above the rim would prevent any possibility of contamination of the fresh water system. Its better then an RPZ (reverse pressure zone) backflow preventer as it provides a positive air gap, much like the spout of a sink faucet does. The requirement being that the spout be at least one inch above the bowl or sink

YES both sides of the manual pumps are contaminated, but the atmospheric vacuum breaker installed connected to the bowl fill after the pump, and mounted high, would prevent cross contamination.
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Old 07-09-2011, 16:36   #11
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Re: Freshwater-Flush Plumbing

I just use the shower head attachment at the sink and squirt fresh water into the head. Of course the seawater intake is closed.
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Old 07-09-2011, 18:05   #12
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Re: Freshwater-Flush Plumbing

They do more than that...they also use solenoid valves that not only open to allow flush water into the toilet, but also keep the potable water OUT when the system isn't pressurized. The only way around that if you connect a manual toilet to the potable water system: NEVER turn off the fresh water pump...make sure the fresh water plumbing remains pressurized at all times.

You're also overlooking the fact that manual toilet pumps are are designed to PULL water through them...pressurized water pushed through a manual toilet pump will mess up the seals, o-rings etc. You could get around that by connecting the toilet intake line to the fresh water plumbing ahead of the pump...but what THAT overlooks is, toilets that are designed to draw flush water

EVERY manual toilet mfr specifically warns against connecting sea water toilets to the potable water system...why? Because they don't want be sued by your heirs when e-coli contamination of the potable water system wipes out your whole crew.

"But we never drink the water from our tanks," you cry. Wanna bet? You wash your hands in it...then pick up a sandwich. You wash dishes in it...rinse out a cup or glass in it before filling with your bottled water. When you wash your face and shower, you get water in your mouth, nose, eyes, ears...some harmful bacteria can be absorbed through the skin...

So...CAN you connect a manual toilet the potable water plumbing? Sure. SHOULD you? I wouldn't...you're the only one who can decide how much risk to your family, friends, crew is acceptable. At least you'll be making an informed decision.
Can you do it? Sure. Should you do it? WHY?
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Old 07-09-2011, 18:07   #13
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Re: Freshwater-Flush Plumbing

That doesn't do the pump any good, 'cuz what goes directly into the bowl only goes through the bottom part of the pump and out the door...leaving the rest of the pump dry...which wears out seals, valves and o-rings about twice as fast as using the pump as it was designed to be used.
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Old 07-09-2011, 18:16   #14
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Re: Freshwater-Flush Plumbing

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That doesn't do the pump any good, 'cuz what goes directly into the bowl only goes through the bottom part of the pump and out the door...leaving the rest of the pump dry...which wears out seals, valves and o-rings about twice as fast as using the pump as it was designed to be used.

I think it's ok Peggy. I only do it when we go to a spot where we run the boat aground, bow in, at one of the Toronto islands. Lake Ontario is all fresh water. But the weeds get sucked in if we use the through hull intake. So we use the shower. But I did not know it might hurt the pump. What the heck, it's only a Jabsco.
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Old 07-09-2011, 18:59   #15
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Re: Freshwater-Flush Plumbing

Actually the atmospheric vacuum breaker (AVB) would be down stream of a solenoid valve of some sort or even a manual valve on the pressure water system. You would use the solenoid valve to fill the bowl, bypassing the manual pump entirely.

The hose down stream of the atmospheric vacuum breaker to the head bowl is not pressurized, it's at atmospheric pressure, and a pretty much a gravity drain to the bowl. It would connect after the manual head pump, in the hose between the pump and bowl.

No way would the head pump survive 40 psig pressure, so water wound be connected after the pump and would be a gravity drain / no pressure after the AVB. You could use a tee in the line between the pump and bowl connection, so one could use a seawater flush if desired.

Basically you would use the fresh water as a bowl fill and then dry flush to clear the bowl as normally done

There might be additional pump o-ring wear, but then your using it to dry flush 1/2 the time anyway..

Actually as the bottom side of the pump is wet from er.. "stuff", the o-ring and sides of the pump body would be wet, so wear would not be that bad. Mainly a little extra wear to the o-ring around the pump shaft I think.

Just to be clear the AVB is an ASSE approved backflow preventer air gap device designed to separate potable from non-potable sources and complies with all building codes. You do need a valve upstream of the AVB to control the water flow

BTW I use my manual head with seawater only. I worked out the safe way for a fellow down the dock. Agree 1000% that you never ever connect potable water to the sea water inlet of the head pump. Totally bad!

Oh, I need to say that I've 30+ years experience as a consulting professional engineer designing plumbing /process systems for just about everything... from large hotel-casinos, to biotech, to boats.

I only look like a blonde bimbo.
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