What to Do If Your Water Heater Starts Leaking (Shutoff Steps + When to Call a Plumber)

A leaking water heater can go from “small puddle” to “major water damage” fast. The good news: there are a few simple steps you can take to reduce damage and keep things safe while you figure out the next move.

This guide walks you through exactly what to do right away, what to check, and when it’s time to call a plumber.

Step 1: Make it safe first (don’t ignore electricity + gas)

Before you do anything else, assume there’s risk around power and heat.

If the water heater is electric:

• Do not touch standing water if there’s any chance it’s near an outlet or the heater’s wiring.

• Go to your breaker panel and turn off the circuit labeled “Water Heater.”

If the water heater is gas:

• Turn the thermostat to “OFF” or “Pilot” (if that’s the lowest setting).

• If you smell gas, leave the area and call your gas provider or emergency services.

If you’re unsure which type you have, look for:

• Electric: no flue pipe on top, usually electrical access panels on the side.

• Gas: a metal flue pipe venting upward and a gas line connection.

  
  

Step 2: Shut off the water supply to the water heater

Most water heaters have a shutoff valve on the cold-water pipe entering the top of the unit.

• Turn the valve clockwise (right) to shut it off.

• If it’s a lever handle, turn it 90 degrees so it’s perpendicular to the pipe.

  
  

If the valve is stuck or won’t fully close:

Don’t force it hard enough to break it. If it won’t close, you may need to shut off the main water supply to the house and call a plumber.

Step 3: Relieve pressure (optional but helpful)

If the leak is active, relieving pressure can slow things down.

• Turn on a hot water faucet somewhere in the home.

• This helps reduce pressure inside the tank and lines.

  
  

Step 4: Contain the water to prevent damage

Water heater leaks often travel farther than you think.

Do what you can quickly:

• Put towels down or use a mop

• Use a wet/dry vacuum if you have one

• Place a bucket under the leak source if it’s localized

• Move items off the floor (boxes, stored items, furniture legs)

If the heater is in an attic or upstairs closet, act fast—water damage spreads quickly through ceilings and walls.

Step 5: Figure out where the leak is coming from (quick diagnosis)

Not all “water heater leaks” mean the tank is shot. Here are common sources:

1) Leak from the top connections

Possible causes:

• loose fittings on the hot/cold lines

• failing flex lines

• leaking shutoff valve

• expansion tank issue

Good news: Often repairable without replacing the whole heater.

2) Leak from the temperature & pressure (T&P) relief valve

This valve is designed to release water if pressure/temperature gets unsafe.

Possible causes:

• excessive pressure in the home

• faulty valve

• failing expansion tank

Important: Don’t cap or plug this line. It’s a safety device.

3) Leak from the drain valve near the bottom

Sometimes the drain valve fails or isn’t fully closed.

Possible causes:

• worn valve

• sediment preventing full seal

  
  

4) Water pooling under the tank (from the bottom seam)

If water appears to be coming from the tank itself, especially the bottom, it often indicates internal corrosion and failure.

This usually means replacement.

Step 6: Decide “repair vs. replace” (the practical rules)

Here are the simplest rules that prevent wasted money:

Replace the water heater if:

• the tank is leaking from the bottom/seam

• there’s visible rust/corrosion on the tank

• it’s older and has recurring issues

• the leak is severe and getting worse

  
  

Repair may be possible if:

• the leak is at a fitting/pipe connection

• the shutoff valve, drain valve, or T&P valve is the source

• it’s a minor leak caught early

  
  

If you’re not sure, don’t guess—misdiagnosing a tank leak can cost you in damage and downtime.

When to call a plumber immediately

Call KLM Plumbing (or a licensed plumber) right away if:

• you can’t shut off the water

• you’re seeing water near electrical wiring or outlets

• you smell gas or suspect a gas issue

• water is leaking into walls/ceilings/flooring

• the leak is coming from the tank body/bottom

• you have no hot water and the leak is worsening

• the T&P valve is discharging continuously

  
  

Waiting can turn a manageable repair into a replacement + water restoration bill.

What to do while you wait for service

If you’ve shut off the water and power/gas, do these:

• Take photos/videos of where the leak is coming from

• Write down the heater’s brand/model and approximate age

• Clear a working path around the unit

• Keep a hot water faucet open slightly to reduce pressure (if safe)

  
  

How to prevent future leaks

A few proactive steps can extend the life of your heater:

• Schedule a yearly inspection

• Flush sediment periodically (especially with hard water)

• Test the T&P valve (a plumber can do this safely)

• Install a drain pan and leak alarm if the heater is inside the home

• Make sure the expansion tank is working properly (if required)

  
  

Bottom line

If your water heater starts leaking, the most important thing is to shut off power/gas and water quickly, then identify whether it’s a connection/valve issue or a tank failure. Some leaks are repairable—but a leaking tank usually isn’t.

If your water heater is leaking, call KLM Plumbing to get it diagnosed and fixed before it causes bigger damage.

Call Today: (252) 607-0375

Service Area: Craven County, Carteret County, Onslow County, Pamlico County, Pitt County