How to Replace a Toilet Fill Valve
If a new flapper didn't fix a running or slow-filling toilet, the fill valve is the next likely cause — still a cheap, DIY-friendly fix.
Before you start: this is general information, not a diagnosis of your specific situation. Shut off water where instructed, take your time, and stop if anything looks different than described here. If you're not comfortable at any point, stop and call us — that's what we're here for.
- 1Turn off the water supply valve, flush to drain the tank, and sponge out any remaining water.
- 2Disconnect the supply line from underneath the tank (have a towel ready — some water will drip out).
- 3Unscrew the large plastic locknut underneath the tank holding the old fill valve in place and lift it out.
- 4Set the new fill valve to the correct height (most are adjustable) so the overflow tube clears the water line with room to spare.
- 5Install the new valve, hand-tighten the locknut underneath (don't overtighten — these are usually plastic and crack easily), and reconnect the supply line.
- 6Turn the water back on, adjust the fill height using the valve's adjustment screw or clip so water stops about an inch below the overflow tube, and test with a few flushes.
If you turn the shutoff valve and it's stuck, won't fully stop the water, or starts leaking around the valve stem itself, stop and call us — a bad shutoff valve is a different, less DIY-friendly problem.
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If this isn't a DIY day, call, text, or book online — same flat-rate honesty either way.