The short answer
When a toilet in a Northern Virginia house won’t flush all the way, the bowl swirls weakly, or the water rises and drains slowly, it’s almost always one of four things: not enough water in the tank, a flapper that drops shut too early, rim holes clogged with mineral, or a partial clog in the toilet itself. All four can be checked in five minutes with the tank lid off. If other drains are slow too, or the toilet gurgles when the washer drains (why a toilet gurgles), it’s the main line instead, and no amount of plunging fixes that.
Is it worth fixing? Yes. A weak flush means double flushing and a plunger by every toilet, and the toilet that half-clogs is the one that overflows. Upstairs, that’s water through the floor and into the ceiling under it. Most of the causes are cheap parts.
Check the tank first
Take the lid off and flush, and watch. If the flush finishes but slow and weak, start with the bucket test in toilet flushes slow or weak.
- The water level. When the tank refills, the water should stop about an inch under the top of the overflow tube, the open pipe in the middle. Many tanks have a fill line printed inside. Lower than that and every flush is short on water. The float on the fill valve adjusts with a screw or a clip.
- The flapper chain. It wants about half an inch of slack. Too much and the flapper doesn’t lift all the way, so it drops shut early and the flush dies halfway. Too tight and it never seals, and the toilet runs (toilet keeps running).
- The flapper. Rubber warps and swells with age. If it’s soft, warped or slimy, a new one is a cheap part at any hardware store.
One quick test: flush and hold the handle down. If it flushes strong while you hold it, the flapper or the chain is the problem.
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Then the bowl
Under the rim is a row of small holes that wash the bowl, and at the bottom of most bowls is one bigger hole, the siphon jet, that starts the flush. Minerals from the water crust them over, slowly, until the flush has no push. Look up under the rim with a hand mirror. If the holes are crusty white or brown, poke each one clear with a small Allen wrench or a bent wire. Pouring a cup of vinegar down the overflow tube in the tank sends it straight to the rim holes. Let it sit an hour, then flush.
If the bowl fills high and drains slowly, something is caught in the toilet’s own trap, the curve built into the porcelain: a wipe, too much paper, a toothbrush cap, a toy. A flange plunger, the kind with a sleeve on the bottom, and 10 to 15 firm pushes clears most of it (how to unclog a toilet). If that doesn’t do it, a toilet auger, never a regular drain snake, which scratches the porcelain. Something hard and stuck sometimes means the toilet comes off the floor.
When it isn’t the toilet
The vent. Every drain stack runs up through the roof so air can get in behind the water. Leaves, a nest or ice in that pipe, and toilets flush weakly, gurgle and drain slowly with nothing clogged anywhere. Don’t go up on the roof for it. A plumber can check it from the cleanout or the roof safely (clogged plumbing vent pipe).
The main line. Other drains slow, the toilet bubbles when the tub drains or the washer empties, water in a basement floor drain. That’s past every toilet in the house (when a slow drain is worth fixing), and if anything’s coming up in the basement, stop running water (sewer backup in the basement).
The toilet’s age. New toilets have been held to 1.6 gallons a flush since the mid-1990s, and a lot of the first ones built that way never flushed well. If yours dates from then and you’ve been plunging it for years, it isn’t you. A toilet built in the last ten years does more with less water.
Swipe to see all columns →
Swipe to see all columns →
| What you see | Usually | Who fixes it |
|---|---|---|
| Weak swirl, tank water looks low | Water level set too low | You, at the float |
| Flushes fine only while you hold the handle | Flapper chain too long, or a worn flapper | You, with a cheap part |
| Bowl fills high, drains slowly | Something caught in the toilet | You with a flange plunger. A plumber if it keeps coming back. |
| Crust under the rim, weak flush | Mineral in the rim holes | You, with vinegar and a wire |
| Gurgles, other drains slow too | The main line | A plumber |
| Weak flush and gurgling, nothing clogged | A blocked vent | A plumber |
| A 1990s toilet that was always weak | The early low-flow design | A new toilet |
Repair or replace
A plumber’s visit to fix a toilet runs $250 to $900: fill valve, flapper, wax ring, or a rebuilt tank. Replacing one runs $800 to $1,300 with the toilet supplied, and there’s $100 off replacing a toilet (current deals). A toilet that’s cracked, rocks on the floor, or clogs every few weeks no matter what is usually the one to replace (what replacing a toilet costs).
SwiftPro sends a plumber, not a generalist, and you get the price before anything comes apart. There’s $50 off any plumbing repair over $400, and the whole-house plumbing inspection is included with any repair, a $149 value (every current deal). If more than one toilet or drain is acting up, a plumber goes through the whole house for a flat $99: valves, drains and water pressure.
Book it
Book a toilet repair. Call (703) 997-9757, or book online from goswiftpro.com/cookiesoffer and a box of warm cookies comes with the visit. Our plumbers work in Oakton, Falls Church, Alexandria, Woodbridge and across Northern Virginia, 24 hours a day. 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 not flushing all the way?
Usually the tank water is set too low, the flapper chain is too long so the flapper closes early, the rim holes are clogged with mineral, or something is partly stuck in the toilet. If other drains are slow too, it’s the main line.
Why does my toilet flush slowly and gurgle?
Gurgling means air is being pulled through the water, which points to a partly blocked main line or a blocked roof vent. If other drains are slow or gurgle too, call a plumber before it backs up.
How much does it cost to fix a toilet that won’t flush right?
In Northern Virginia, a toilet repair at SwiftPro runs $250 to $900, depending on the part. Replacing the toilet runs $800 to $1,300 with the toilet supplied.
Can I use a drain snake on a toilet?
Use a toilet auger instead. A regular drain snake scratches the porcelain. The auger has a sleeve that protects the bowl.
