The short answer
A toilet tank that won’t fill, or takes minutes to refill, in a Northern Virginia home is almost always the water getting to it or the fill valve letting it in. Start with the shutoff valve on the wall behind the toilet, which should be open all the way. Then look at the fill valve, the float and the supply line. If the sinks and the shower are weak too, it isn’t the toilet at all. It’s the water pressure for the whole house.
Seven checks, in order
- The shutoff valve. Turn the valve behind the toilet counterclockwise until it stops. Someone may have turned it partway down to stop a hiss. On older valves with a round handle that takes several turns, the washer inside can break off and block the flow even with the handle wide open.
- The float. If the tank fills but stops low, the float is set too low and every flush is weak. Raise it until the water stops about an inch under the top of the overflow tube.
- Something stuck. The float can catch on the tank wall or the flush lever arm. Lift the lid and watch it fill. It should rise freely.
- Grit in the fill valve. After the water company works on the main, or after a plumber shuts the water off, sand and rust can lodge in the fill valve. On most modern fill valves, turn the water off, twist the cap off the top, hold a cup over the opening, and turn the water on for a few seconds to flush it out.
- A worn fill valve. If it fills slowly, hisses, or sometimes won’t shut off, the valve is worn. It’s a common part, and a new one is quieter and faster.
- The supply line. A kinked line, or an old one narrowed by buildup, can slow the fill to a trickle. Braided steel lines are cheap to replace.
- The whole house. If every fixture is weak, look at the house, not the toilet.
A fill valve that’s on its way out often makes noise before it quits. Toilet making noise covers the hiss and the whistle.
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When the whole house is the problem
Weak water at every faucet in the house points at the plumbing, not the toilet. The usual causes here are a pressure reducing valve that’s failing where the water comes in, a main shutoff that isn’t open all the way, or old galvanized steel pipe closed down by rust from the inside. Houses built through the 1960s in Northern Virginia often still have some of it. Low water pressure in the whole house walks through each one, and pressure reducing valve explains the valve.
Galvanized pipe rusts from the inside, so the opening gets a little smaller every year and every fixture on that line fills a little slower. That’s the kind of repair that’s better found early, before the pipe starts leaking too.
Tank fills, bowl doesn’t
If the tank fills fine but the water in the bowl sits low, that’s a different problem: the small refill tube, a partial clog, or a blocked vent. Toilet bowl water level low covers it.
What to check before you call
- Is the shutoff valve behind the toilet all the way open?
- Does the float move freely when you lift it?
- Are the sinks in the same bathroom strong or weak?
- Did anyone shut the water off at the main lately? Where your shutoff valves are, if you’re not sure.
If the valve behind the toilet won’t turn, don’t force it. Old valves crack and then leak all the time. Shut the water off at the main and replace the valve instead. When the main shutoff itself needs replacing.
A slow toilet tank is one of the early signs that something upstream is wearing out. Every warning sign around the house, from a furnace’s blinking light to the sounds a house makes, is in one guide.
Fix it small, fix it now
A leak caught early is cheaper three ways. The water and sewer bill stops climbing. The water stops soaking the subfloor or the ceiling under it. And it stays a small repair, a part and an hour, instead of a bigger one later. Almost everything we find wrong with a toilet is repairable, and once it’s fixed right, you stop checking the floor every time you walk in.
What it costs when we fix it
Most leaks, wobbles and fill problems are a repair, toilet repair at $250 to $900, with the price in writing before we start. That covers a wax ring, a flange repair, tank bolts and gaskets, and fill valves. When the toilet itself is cracked or worn out, a new one installed runs $800 to $1,300, and this month’s coupons on our offers page take $100 off a new toilet, or $50 off any plumbing repair over $400. Any plumbing repair also comes with a whole-house plumbing inspection, a $149 value. If you can’t tell where the water is coming from, leak detection runs $200 to $500. A plumbing diagnosis visit is $49, or $250 after hours.
Call (703) 997-9757, day or night, or book a toilet repair online. Rated 5.0 stars across 1,138 reviews on Google, Angi, Yelp, the BBB and Facebook, Virginia Class A license 2705192276.
Questions people ask
Why is my toilet tank not filling?
Most often the shutoff valve behind the toilet is partly closed, or the fill valve is clogged or worn. If every faucet is weak too, it’s the house water pressure.
Why does my toilet tank fill so slowly?
Grit in the fill valve, a worn fill valve, a partly closed shutoff valve, or a kinked supply line. Flushing the fill valve clears most grit.
How do I clean a toilet fill valve?
Turn the water off, take the cap off the top of the valve, hold a cup over it, and turn the water on for a few seconds to flush out the grit. Then put the cap back.
Can low water pressure make a toilet fill slowly?
Yes. If every fixture is weak, look at the pressure reducing valve, the main shutoff, or old galvanized pipe.
How much does it cost to fix a toilet that won’t fill?
Often it’s a fill valve you can fit yourself. When we do it, toilet repair runs $250 to $900, priced in writing before we start.
