Side of the house, stop 3 of 4

The pipe coming down from your water heater

The water heater relief valve pipe carries hot water away when the tank’s relief valve opens, so its end has to stay open. Never plug or cap it. If it’s dripping or the end is wet, get a plumber, and stay clear because hot water can scald.¹

Stand in the doorway of the water heater closet or garage and follow the pipe from the brass valve near the top down to where it ends.

Updated November 4, 2026, Midlands House Walk

Don’t put a cap, plug or bucket-and-hose fix on this pipe, even if the drip is annoying. It’s there as a way out for hot water, and the drip is telling you something’s wrong.

Copper pipe running from a brass valve down the side of a white tank water heater to just above a drain pan — Follow the pipe from the brass valve down the tank. This one stops just short of a drain pan. AI-generated picture.

Short green-patinated copper pipe coming through a brick wall low down, pointing at mulch — A short copper pipe through the brick, low down, aimed at the mulch. Some heaters send their relief pipe outdoors like this. AI-generated picture.

Does it end outdoors?

Look for: Check the outside wall near the heater closet, low down. Look for a stub of pipe, and for stains, wet mulch or worn soil beneath it.
What it tells you: Wet ground under it means the valve has let water out, or is leaking. Keep children and pets clear and tell a plumber. Where yours ought to end is one to ask a plumber or the local building office.

Water heater in a plastic pan inside a closet with a louvered door standing open — A closet heater in a pan. Check for drips under the end of any pipe that comes down the tank. AI-generated picture.

Does it end at a pan?

Look for: Look at the pan under the pipe end for water, drip marks or mineral crust. Leave the gap below the pipe open and clear.
What it tells you: A wet pan could be this pipe or the tank itself, and a plumber can tell which. Fix leaks early, because damp in a closed closet stays put.³ The water heater stop covers the rest of the closet.

Garage corner with a white water heater on a low wood stand and household clutter nearby — A garage corner, where things get stacked. Whatever is on this pipe’s route should move. AI-generated picture.

Is anything blocking the run?

Look for: Walk the full length with your eyes. Look for kinks, boxes pressing on it, or a cap or plug someone has added at the end.
What it tells you: A cap, a plug or a crushed section means the pipe can’t do its work. Don’t try to clear it yourself. Book a plumber today and say what you found.

Copper water lines soldered into a brass valve with a dark lever against a pale wall — A shutoff like this isn’t the relief valve. Know both before anything drips.

Do you know where the water shutoffs are?

Look for: Find the valve for the heater, often above it,² and the main shutoff for the whole house, while everything’s calm.
What it tells you: If the pipe is running hard or steaming, the tank may be overheating: get everyone away from it and call 911 from outside. A slow drip is the one to phone a plumber about, and knowing your shutoffs helps with that call.

Should you test the valve yourself?

No test steps here, on purpose. What comes out is hot, and CPSC puts third-degree burns at 2 seconds for 150°F water.¹ That lever is for a plumber to work.

Yours to do

Follow the pipe and learn where it ends.
Keep its end and the space below it clear.
Note any drip, stain or crust, with a picture, for the plumber.

For a licensed pro

Any drip or wet end at all.
A new relief valve, or a pipe that’s capped or kinked.
Any testing of the valve. See who to call.

Where this comes from

Keep walking (AI picture)Foundation vents: open in summer, closed in a freeze?