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Old 01-10-2017, 12:18 PM   #1
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Fresh Water Head Conversion & Contamination

I've read some of the prior threads on this topic... and am interested in doing this myself.

Coming from the RV world, every single toilet on the road is connected, in a lot of cases without even a backflow preventer, to the pressurized fresh water system... and of the 10 million or so RV owners in the US.. no one seems to be getting sick.

So, I must be missing something - please without pontification or doomsday advice... can someone point to cases of contamination actually happening and if so, root cause?
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Old 01-10-2017, 02:00 PM   #2
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Cant document the contamination statistics but my last 5th wheel toilet and my current RV toilet on the boat both have the integrated backflow preventers (siphon breakers) you discuss that are factory installed.


Easy enough and cheap enough to install one.
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Old 01-10-2017, 02:17 PM   #3
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Backflow prevented isn't a siphon break, it's just a one way valve. You'd need both. Toilets that are designed to be connected to the potable water supply require pressurized water and have the siphon break built in. The backflow preventer is typically a solenoid valve in the flush water inlet line, although some toilets including VacuFlush have a "water valve" at the back of the bowl.
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Old 01-10-2017, 05:52 PM   #4
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Peggie, hi - have your kindle book, thanks for chiming in -

backflow valve is your belt and the siphon break is "suspenders" for when no freshwater pressure? (pump is off)

Again, have not seen this level of redundancy on land. I mean.. think about a residential toilet. Really neither of those devices are in play. Its just gravity, aka pressure.
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Old 01-10-2017, 06:28 PM   #5
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Fresh Water Head Conversion & Contamination

Correction kev_rm: Every residential and commercial toilet has a vacuum breaker or air gap incorporated into it.

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Old 01-10-2017, 06:32 PM   #6
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think about a residential toilet. Really neither of those devices are in play. Its just gravity, aka pressure.

The difference is, on land flush water is delivered to a tank above the bowl, so the fresh water plumbing never comes in contact with the bowl. The flush water line in a marine or RV toilet is connected directly to the bowl. Without the necessary vacuum breaker and backflow preventer, e-coli and other bacteria in the bowl can migrate into the fresh water supply.
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Old 01-10-2017, 06:42 PM   #7
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Correction kev_rm: Every residential and commercial toilet has a vacuum breaker incorporated into it.

Nope...residential toilets that have a tank don't, and commercial toilets to which flush water is fed directly to the bowl don't either because the water supply is always pressurized...which essentially creates a backflow preventer. But on a boat or RV, the fresh water system is pressurized only while the water pump remains on.

I don't see a vacuum breaker in your drawing of a commercial toilet...and your drawing of a residential toilet is only the tank....and the flush valve is a flapper valve that's lifted when the toilet is flushed. So even if the tank overflows, there's no the water pipe that feeds the tank can feed the bowl directly.

I have 3 toilets in my house, all of different ages (house is 30 years old), all with different flushing mechanisms in the tank...the only flush valve in any of 'em is a rubber flapper valve in the bottom of the tank. On all of 'em a chain or a rod on an arm that the flush lever raises lifts it. And the ball cock only prevents the tank from overflowing by shutting off the flow of water when the correct level in the tank is reached. If it overflows, the floor gets wet...there's no way that water in the toilet bowl can ever get into the water plumbing.
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Old 01-10-2017, 07:15 PM   #8
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The residential (or commercial) water supply is not always pressurized. The pressure can fail because of equipment failure, broken pipes or even intentional shutdowns for maintenance. This is why appliances including toilets have built in cross contamination features and why backflow preventers are recommended and sometimes required for outside faucets and irrigation systems.


Anyone who would ignore the possibility of cross contamination on his or her boat is a fool and a soon to be very sick fool. Install nothing that isn't designed from the factory for pressurized fresh water if fresh water flushing is what you want.
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Old 01-10-2017, 08:39 PM   #9
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Quote:
Originally Posted by WesK View Post
The residential (or commercial) water supply is not always pressurized. The pressure can fail because of equipment failure, broken pipes or even intentional shutdowns for maintenance. This is why appliances including toilets have built in cross contamination features and why backflow preventers are recommended and sometimes required for outside faucets and irrigation systems.


Anyone who would ignore the possibility of cross contamination on his or her boat is a fool and a soon to be very sick fool. Install nothing that isn't designed from the factory for pressurized fresh water if fresh water flushing is what you want.
If you're going to call people names, give me ONE EXAMPLE of someone getting sick and their system design that contributed to it.
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Old 01-10-2017, 08:47 PM   #10
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Quote:
Originally Posted by HeadMistress View Post
think about a residential toilet. Really neither of those devices are in play. Its just gravity, aka pressure.

The difference is, on land flush water is delivered to a tank above the bowl, so the fresh water plumbing never comes in contact with the bowl. The flush water line in a marine or RV toilet is connected directly to the bowl. Without the necessary vacuum breaker and backflow preventer, e-coli and other bacteria in the bowl can migrate into the fresh water supply.
I don't know, this is pedantic but there is a path... its just uphill. it doesn't get dry in between flushes..
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Old 01-10-2017, 10:18 PM   #11
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Anyone with basic skills can redesign head systems...as long as a few basic principles are applied.


Some people are skeptical that others have brains.


But it is important to understand the basics and hw to prevent cross contamination of water sources.


To me it is the most basic of all systems on a boat.
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