Commercial toilet in residence.

[LiQuId]

Originally Posted by phishfood

Actually, if I were attempting this, I would in fact run a 1" line from the bladder tank to the flush valve. Those water closet flush valves demand a lot of water in a very short time span, and I would bet that a 3/4" line wouldn't deliver enough.

I can't think of a reason that you would need a backflow preventor on the tank.

You would be correct, our code here says that the minimum soze for a flush valve W.C. is 1".

...

I wouldnt think you would need a check valve to the toilet, but I;ve not installed a commercial toilet withing a residence and have never had need for a bladder tank, I will let others chime in on this one as I've always had a sufficiantlly sized line to work with. As far as the pressure goes, this shouldnt be the cause of the problem, and you definatelly dont want pressures to exceed 80 psi ... 75 is even up there.

[Dollar_Bill]

I mentioned 75 psi because that is available where the supply comes in. I will reduce that pressure to a more appropriate amount. I have more than enough pressure, just need to up the volume.

[Caduceus]

My thoughts...1. Installing a backflow preventer before the pressure tank on the branch and increasing the pipe diameter to 1" would be an attempt to duplicate the effect of a dedicated 1" service line to supply the flush valve. The branch would maintain the pressure in the line separately from the rest of the water system and hopefully provide much needed volume through the 1" piping. The down side to this is that a higher pressure in the 1" piping, due to the pressure tank, may cause to back flow preventer to close prematurely and not allow enough water in from the existing 3/4" line even when the toilet is flushed, because of the quick action of the flush valve. The pressure tank would need to be adjusted to match or be slightly lower than the incoming 3/4" pressure at the point of connection.
2. Though, without a check valve, a pressure tank may provide enough pressure throughout the entire water dist. to give the 1" just the kick it needs to create the same effect as a 1" service...both pressure and volume.
Curious to see how this all turns out, Dollar. Let us know.

[LiQuId]

Your problem is Volume, not pressure, the pressure remains the same in a flushometer on both sides of the diaphragm, its the relief port that restores the equal pressure and seals the valve. You need Volume, what is happening with the 3/4 Urinal flushometer is that you are not getting enough volume to induce a syphon, flushometers are designed to operate on less water than conventional toilets but do require the line to be properly sized for their application, Im not saying "it cant be done" but I wouldnt do it.

If I were to ( hypothetically ) do this, I would be looking at a scenario of "how can I get enough water to this", and that again takes me back to volume.

holding vessel, perhaps a expansion tank with a bladder...

[Dollar_Bill]

Originally Posted by phishfood

Actually, if I were attempting this, I would in fact run a 1" line from the bladder tank to the flush valve. Those water closet flush valves demand a lot of water in a very short time span, and I would bet that a 3/4" line wouldn't deliver enough.

I can't think of a reason that you would need a backflow preventor on the tank.

Got the bladder tank installed and it works great! Wife is happy. Simple installation. To recap.

A commercial toilet needs a 1" supply line at about 70psi to operate the flush mechanism. I have a 3/4" water supply line coming in to our home at 70psi.

Toilet would not flush. Not enough water to initiate the siphon to get the toilet to work.

The pressure/bladder tank with a 1" inlet/outlet valve. I placed this in the attic above the toilet. I use CPVC for cold and hot to simplify, so I had to transition to the 1" PVC. I brought a 3/4" line into a "T", this allows the water to flow into the tank, the toilet valve temporarily blocking the flow to the toilet.

http://www.hardwareworld.com/Vertical-Pressure-Tank-42-Gallon-Equivalent-pEC0QRQ.aspx

The water flowing into the tank caused the air-filled bladder to compress until the pressure on the water was at about 70psi, I guess. That is the pressure where the supply enters our home. The tank system is rated at 100psi.

When I flushed the toilet, a stream of water came down the 1" pipe at 70psi (or so) and the toilet flushed very well. The pressures equalize so there is no back-flow. I do have an anti-back-flow valve where my supply line comes into the home.

There was a small leak, but I fixed it.

[Nathan_G_Apeman]

I have had the same type of problem as this. I found a great site with hard to find urinal replacement parts...

http://govex.ngap.com/search.aspx?keyword=urinal&soption=2&ProductCount= 60

...they have great customer server too.

I looked everywhere for one of these...

http://govex.ngap.com/product.aspx?zpid=2263024

...it isn't a 1" flush valve though. I'm sure they have those too.

[Dollar_Bill]

Thanks for the additional info, Nathan.