Toilet for Low Pressure House

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Pablo Rodriguez

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This is a bit of a continuation to another thread I created ~9 months ago where I was looking for a toilet to use at an off-grid property where the water fed to the house is from a water tank where the head of pressure equates to ~5psi to the house. In looking at ways to boost that (pressure boosters mainly), I haven't found a cost effective way to do that and have thus not purchased or installed a toilet to the property. In researching what may work with such limited pressure, I wanted to get thoughts on different systems out there and whether there's an option available here.

House details: water tank fed, 5psi pressure at inlet to toilet, septic system ~20ft from house, 4in drain line, construction ~1982, 10" rough-in

I really, really liked the Glacier Bay vacuum-assist offered through Home Depot but they only make it as a 12" rough-in! :( Basically, I want a 10" system that's as-good as that Glacier Bay is purported to be.

System #1: Niagara Stealthflush - Vacuum-assist at 0.8 GpF (MaP rated at 800) - clearing the trapway seems fine but worried about moving waste down the line at only 0.8GpF.

System #2: American Standard Cadet 3 at 1.6 GpF (MaP rated at 1000) - this seems like a really good option... highly rated, but risk in clogs at such a low pressure?

System #3: Fine Fixtures / Swiss Madison Washdowns at 1.6 GpF (no MaP rating) - I like the washdown options and don't mind the "cleanliness" issues so much (multiple flushes, cleaning often... not a bother). Install seems more difficult for a layman and the lack of a MaP rating is strange... am I missing something to these systems?

Appreciate any help the community could offer!
 

breplum

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The flush is NOT dependent upon the fill pressure of the water supply IN ANY WAY on any WC/toilet
Water supply pressure only comes in to play when filling the tank, period. It will take forever for your tank to refill.
That GB WC uses a simple Fluidmaster style ballcock, same as the AS one uses.
I have no experience on how long it takes but eventually should refill the tank and bowl and shut off when the tank is full.
I have the AS Cadet3 FlowWise 1.28GPF (also MaP rated 1,000) and highly recommend it. It has never clogged on me.
I always recommend getting rid of 10" rough and converting to 12" to allow widest options on WC choices.
 

Pablo Rodriguez

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breplum - Thank you for the reply. That's good to know that the only pressure that "matters" is the local to the toilet when a flush is initiated. And, yes, the fill time is going to be a pain... and you bringing that up makes me question the washdown units as no courtesy flush would be possible until 10-20 minutes later. It sounds like the Cadet could be a good option and I'll start looking into whether the drain pipe could be slightly modified to fit a 12" rough-in.
 

jadnashua

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It depends somewhat on the fill valve involved...some can need a minimum pressure to function, but a gravity flush toilet doesn't need water pressure to flush.
 
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