Water heater leaking from the drain valve
The cheapest fix on the heater
This is the cheapest leak a water heater has, and it is the first thing to rule out before anyone tells you the tank has gone. The drain valve is the spigot near the floor. A worn washer, trapped sediment, or a valve left slightly open after draining will all drip.
The water leaving a drain valve is tank temperature — 120 °F or hotter. Do not put a hand under it.
How to tell it's this
- You can trace the water to the spigot itself, and the tank shell above it is dry.
- The floor is wet in a line leading away from the valve rather than pooled all around the base.
- Someone drained or flushed the tank recently.
- A drip that gets briefly worse if you nudge the handle.
What to do
- Check it is fully closed first. Turn it gently clockwise — gently, because plastic valves crack.
- If it still drips, put a bucket under it and note whether it is a drip or a run.
- Have a plumber replace the valve. Ask for a brass one; the plastic originals are what fail.
- Do not force a brittle plastic valve. If it cracks under pressure it will empty the whole tank onto the floor.
What it costs
With a plumber
Replace the drain valve
$150–$300
installed
Part only
If a pro is already on site
$10–$25
the part itself
Typical US ranges for 2026, not quotes. Labour is 30–50% of an installed price, so where you live moves these numbers more than anything else does. Get two or three local estimates.
If that's not it
The valve is dry and water is coming from under the tank itself
A tank that has rusted through →
It is a slow drip you cannot trace to any fitting
A slow leak from underneath →
Not sure which of these it is?
Answer four questions — where it's leaking, tank or tankless, gas or electric, and how
old it is — for a specific cause, a repair-or-replace call, and a cost.