Toilet Cistern Valve Not Shutting Off

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tygertung, Oct 31, 7:23am
At my child's kindergarten there are some chickens and I have installed a rainwater tank to collect drinking water for them.

I have built one of those automatic chicken waterers which is made out of a 20L drum with holes in it for the chickens to put their heads through and the water level is supposed to be about 1cm below the holes.

I have installed a toilet cistern valve to control the water level in the drum, but there seems to be a problem with it not shutting off properly; the water level seems to just slowly rise and then it will dribble out the holes.

Is there a problem with these cistern valves with the ultra low pressure from the rainwater tank?

There is very little head, as the bottom of the rainwater tank is only about 300mm off the ground. The rainwater tank is filled up almost to the top as I filled it with the hose and we have had a little rain.

I initially bought a cheap valve from trade depot which leaked, so I bought a more expensive one from mitre 10 and that still seems to be leaking!
There isn't really enough room in the tank for those old-skool large brass ballcocks.

lythande1, Oct 31, 7:38am
The water level in the tank is controlled by an adjustable float. A float that's set too low produces a weak flush; if it's set too high, water spills into the toilet overflow tube and the fill valve won't shut off. . If not and the toilet keeps running, adjust the toilet tank float up or down.

Better though is to have some check on chickens every day, not make automatic things and leave them to it.

tygertung, Oct 31, 7:42am
The float is set lower, but the water is coming out.

The chickens are checked on every day, but this scheme is good to ensure they get a fresh supply of water constantly, not just once a day.

5425, Oct 31, 8:26am
Does the ball have the required distance to travel during the cycle?. eg 100mm

tygertung, Oct 31, 8:35am

pauldw, Oct 31, 9:13am
Low pressure should make it easier to shut off. As it is rain water is there something like bits of leaf stuck in the valve? The low pressure may not clear any blockages.

tygertung, Oct 31, 11:29am
The valves have a filter going into them so shouldn't be any leaves stuck in them.

budgel, Oct 31, 12:25pm
Operate it manually to see if it shuts off when you lift the float. You could take the valve apart and inspect the washer. Turning the washer over is often an easy way to get it working if you dont have a replacement one handy.
Can you turn down the inlet tap a little?

trade4us2, Oct 31, 4:08pm
You should have a filter in the valve. Otherwise it is faulty.
I can't see the mitre10 link. Their computer does not appears to be working.

tygertung, Oct 31, 10:29pm
It is brand new so should be OK surely?

There isn't an inlet tap as it isn't in a toilet cistern.

pauldw, Nov 1, 3:34am
Have you tried setting the initial shut off level slightly lower? Sometimes the shutoff has a bit of creep upwards.

tygertung, Nov 1, 7:55am
Yes, I have adjusted it so that the float is well underwater. The entire float is at least 2cm under water now.

supernova2, Nov 5, 5:55pm
That's the problem the float has to be on top of the water. You have got this valve attacked to the bottom of the tank vertical?

m16d, Nov 5, 5:59pm
Ask all your kindy kids.
Is anybodys Dad a plumber.

tygertung, Nov 5, 6:18pm
No, the float is at the top, but the water level keeps rising above the level of the float.

tweake, Nov 5, 6:58pm
you have a leak. either the seal or the pipe fittings.
tho i would use a ballcock valve as it can put a lot more pressure on the seal.

pico42, Nov 6, 9:09am
That’s not right.

Drain some water out, so it’s well clear of the float. Operate the float by hand and check it shuts the water flow off. If it does, there is a leak elsewhere in the system letting water in. Find where it is.

tygertung, Nov 6, 1:41pm
There isn't, this is the second float valve I've tried, both new. There must be something about the pressure being too low, strangely. I don't know how the valve mechanism in these things works.

tweake, Nov 6, 4:18pm
i doubt its due to low pressure, i suspect its more to do with being a large valve and not being used much. its not being used like a toilet where all the water empties and the valve opens right up and refills it. in your case the level goes down a tad and the valve opens up a tiny bit to refill.
the trouble with that is the valve can stick and get bits of dirt stuck under the valve. the valve is not getting the water flow to clean it self.

i would at least pop the top off and clean the valve seal.
finding a much smaller valve would probably help.

tegretol, Nov 6, 8:28pm
I believe that those ballcocks need more than a dribble of pressure to fully seal. The pressure behind the seal actually presses on the inside of the bore to create the seal and without that pressure (?even 1psi) then it may leak. Just a thought but OP - I suspect that you have insufficient pressure (head) of water to make the seal work.

tygertung, Nov 7, 7:26am
I think so too, as this is the second one which didn't work. The first one was a cheap one from Trade Depot which didn't seal, and so I bought a more expensive one from Mitre 10.

There is very little head.

I think I need an old style ballcock, but one which the lever arm isn't too long.

I don't think there is any debris stuck under the seal as there is a filter going into the cistern valve; it is built in.

pauldw, Nov 7, 7:54am
Have you had a look at your valve? I have a Caroma/Geberit style here and it is simply a silicone diaphragm that gets pushed onto a plastic nipple by the float lever. The old style ballcocks usually had removable stainless nipples so you could adjust flow/noise to suit water supply. This could result in a slow leak if the nipple wasn't screwed in properly even if the sealing washer was OK.
If the seal depended on water pressure how would a light float open a valve?

tygertung, Nov 7, 8:47am
I have tried two different brand new normal modern toilet cistern valves. Both have the same issue. They seem to be 100% plastic so not obvious how to disassemble, but they are brand new so theoretically be OK.

pauldw, Nov 7, 9:39am
Are you mounting the valve so it is vertical? Any tilt could reduce the effectiveness of the float acting on the seal.

tygertung, Sep 12, 11:44am
Yes, it is vertical.