[brucelaidlaw]

I have a Fluidmaster (400UK) ballcock in my cistern. I want to use a rainwater tank to fill it just using gravity. The tank's 3 or 4 feet higher but the water won't run in. I've read in this question (https://www.askmehelpdesk.com/plumbing/toilet-cistern-slow-fill-350059.html) details on how to replace the washer, and I've taken mine apart. But there seems to be a very small pinhole for the water inlet. If I make the hole in the washer bigger then it won't shut off when the float rises? Any ideas? Thanks

[creahands]

Do u get water with to cap of ballcock removed?

My guess is that u have sediment from rain water clogging line.

Are u filtering water between rain tank and toilet? If add filter to system, may solve problem.

Good luck

Chuck

[speedball1]

I want to use a rainwater tank to fill it just using gravity. The tank's 3 or 4 feet higher but the water won't run in

Even at 4 feet elevation your head pressure's only 1 3/4 PSI. Ballcocks are designed for a higher pressure and if you open up the hole in the washer all you're going to do is destroy the washer. Tie the ballcock into house pressure. Good luck, Tom

[creahands]

Hi Tom

Thanks for getting me straight.

Chuck