View Full Version : Fill Valve Recomendation for Low H2O pressure

06-27-2012, 09:07 PM
Hi all,
I'm part owner of a remote family cabin in the Sierras that gets its water (indoor plumbing) via a 1.5" pipe that goes up a steep hill behind the cabin about 40 to 50 ft or so and connects to a pipe inlet at the base of a a small homemade concrete dam. We have used this setup for decades and for the most part, its worked fine for supplying cold water for a kitchen sink, bathroom sink and toilet. Though as you'd expect, the pressure is much lower than a municipal supply, and no, I don't know what the pressure is. We put in a "new" (actually an old one, circa 1958) replacement toilet last weekend as the old one was not filling reliably anymore and it looked pretty bad. The replacement toilet has one of the ubiquitous modern Fluidmaster plastic fill valves. The tank wouldn't fill up at all with this type of fill valve. By taking it apart and studying the design of it, I was able to get it to fill slowly though (about 5 minutes to fill up), by filing off some of the rubber on the top seal to make it less stiff, so it could open with the lower water pressure. It seems to be working fine so far (tested it with many flush and fill cycles), but I'm not sure of its long term reliability. On my next trip up there, I'd ideally like to replace it with a new fill valve that is better suited for low water pressure conditions. Does such a thing exist? What do you recommend? It would also be nice if the toilet tank could fill faster, though we've coped with a slow filling tank for a long, long time. Also, as you might expect, sediment builds up in the pipes in between visits and I'm concerned that the Fluidmaster valve, with its small internal ports, could be prone to plugging up. Any help would be greatly appreciated!

Gary Swart
06-28-2012, 10:59 AM
I suppose your reason for using an outdated 1958 toilet was to save money. Understandable, but this toilet requires at least 3.5 gallons of water to fill, and very possibly as much as 5 to 7 gallons! A new low flow toilet such as the Toto Drake II would require only 1.28 gallons of water. Perhaps saving water isn't a major concern, but think about how much stress you are putting on you septic system. I would suggest that rethinking the cost of a decent quality toilet is in order. BTW, a pressure gauge is cheap and easy to use.

06-28-2012, 01:16 PM
Many fill valves need about 20 PSI to operate. You may want to look at a ballcock, fill valve with ball on an arm.

06-28-2012, 02:52 PM
50 feet od head give you about 22 PSI. 40 feet is about 18 psi

06-28-2012, 03:04 PM
He said the pipe "goes" 40 or 50 feet, not that it goes UP that distance. A fill valve with a float ball will operate and any pressure.

03-15-2013, 05:16 AM
He said the pipe "goes" 40 or 50 feet, not that it goes UP that distance. A fill valve with a float ball will operate and any pressure.

I found this thread while searching online for minimum pressure to fill a standard toilet. The toilets I saw in the country seemed like the same type I have in my house and my parents house which has a float ball valve.

Let me give you a quick background. I recently volunteered on a residential design project in Haiti. The community wanted to have "flush toilets" as opposed to the more standard pit latrine. I tried to design a system that would work off of collecting the grey water from a cluster of houses into a storage tank and then feeding that downhill to the toilet. Each cluster of houses is served by an outhouse with two flush toilets. Everything has to be gravity fed because the use of pumps is too expensive. I currently only have 6" of rise from the top of the toilet tank (approx 3.5' above the ground, including a 1' structure foundation) to the base of the storage tank.

Will that work?

03-15-2013, 07:45 AM
Since most 'float type" fill valves are a simple open/close device the incoming pressure is only a factor to determine how long it takes to fill the tank. Your "pressure" depends on how high the water level is, not the bottom of the tank.