Pressure assited toilets: best supply pressure and outflow pipe joint stress

[flitch plate]

Folks ... I am unhappy with my low volume gravity assisted toilet (A.S.-Cadet); it simply will not clean the bowel and so requires additional flushes and hand cleaning after use. Since I can't buy a toilet over 1.6 gpf, I think pressure assisted maybe the answer. Considering a Kholer Wellworth because of the specs that sound good:

- floor to rim height (15.5 in for short people; with seat its on the low side of comfort range)
- surface area of the water - 10 x 12 would seem to mean better coverage of side walls and higher volume in bowel
- 1.6 gpf largest volume available
- trap diameter seems competitively wide and so a strong outflow to carry solids
- elongated bowl easier for overweight folks and men
- further distances of water surface from bowl lip (farther from the splash)
- quality of and performance of pressure assisted system
- no more tank condensation; dripping on the floor
- quality of the control valves? I am not sure

I have a well and a septic tank situation; all are brand new. Here are my questions:

1. What about the flush force into my PVC 4" drain (I am properly plumbed with long sweeps not san-T's) ? Do I need to strengthen the pipes with more hangers? is rigidity of the hangers an issue?
2. My supply pressure into house is set for 85psi but its head drops considerably through a whole house sediment filter, various elbows, a manablock and interior 1/2" pex. What is the realistic minimum water pressure necessary for pressure assisted toilet systems (Slone Flushmate)?
3. Are my assumptions correct re: features of the Wellworth?

 

[Reach4]

1. It is not going to pressurize the drains because the flows are open through the bowl.

2. https://www.flushmate.com/installation/ says "between 20 P.S.I. to 125 P.S.I. for FLUSHMATE® III and between 25 P.S.I. to 125 P.S.I. for FLUSHMATE® IV. "

 

[Sponsor]

 

[WJcandee]

The Flushmate unit accumulates pressure within it, so as Reach4 points out, it can accept a wide range of input pressures. This isn't a flushometer, which doesn't accumulate pressure and thus requires a certain amount of pressure and flow to be available for the flush when the handle is pulled.

In your list of desireable specs, things like elongated and condensation aren't usually an issue in modern low-flow gravity toilets. You can get plenty of elongated gravity toilets, and condensation is very rare in those Totos, for example, which use only half the tank in the flush and retain the rest for weight, so the tank refills basically with the room temperature water that is sitting in the pipes, and mixes with the room-temperature water that is sitting in the tank already. Unless it's a high-volume application, we don't usually see condensation. And the 1.6 versus 1.28 issues are long over in most Totos and other top brands -- the extra quart adds basically nothing, certainly not to the flush effectiveness in any meaningful way. Much of it comes from a different water spot and more-finely-calibrated refill.

The only issue that I can think of that might come into play in a normal application is that the rush of water might be a little faster than a gravity, and so might be more likely to require a DWV system that is properly-vented. In other words, it might siphon your shower trap or lav trap if those aren't properly-vented. Most are, but we regularly see "homeowner-engineered" hookups where they leave the vent out or pull the shower through an illegal heel inlet into the closet bend, and those are going to be more inclined to siphon in the face of the slightly-faster rush of water coming from a pressure-assist.

I'm also not sure that pressure ipso facto means bowl cleaning, as there are gravity toilets that have good bowl cleaning and stick-resistant surfaces, but why don't you let us know how it turns out for you!

 

[flitch plate]

Thanks you, Wise One, and Reach4, for bringing me up to date on the issues (or non-issues, I guess) and correcting some myths of mine.

I have a 4" toilet drain recently plumbed with a long sweep into the 4" horizontal main soil pipe, with a couple of AAV's and a roof-terminating vent within a few feet of the toilet. Currently our Cadet 3 gravity feed toilet evacuates fine, but does not get a clean bowl. I wish I had 12" not 10" rough, to get more new toilet options. We have lactose intolerant/celiac other digestion problem users who have gas explosions and sticky feces texture issues. The primary issue is the bowl does not get clean (solids, etc drain fine, but bowel is left dirty and has to be cleaned after use).

I looked at AS, Gerber, Kholer options and landed on the Gerber Ultra Flush (10" rough is the limiting factor) - they can mix bowls and tanks to get these features:

- pressure assisted (assuming its gets the bowel cleaner)
- 12" X 10" water surface area (assuming less chance of dirty walls, largest water surface area I could find)
- 1.6 GPF (assuming more water means longer washing period and better coverage)
- bowl walls cleaning with water jetted from rim
- elongated (more room for hanging junk)
- 3-1/8" trap
- not too high a rim (the 17-18" rims with seat are too tall for my wife)

http://www.gerberonline.com/downloads/productliterature/other/GRBR_Performace_2014.pdf