Ask how much water, from where, and whether it is near anything electrical. Then talk them through shutting it down safely while they wait.

Is a Leaking Water Heater an Emergency, or Can It Wait Until Morning?

Treat it as tonight if water is spreading across the floor, coming from the tank itself, or getting near outlets, the panel or other appliances. A slow drip from a fitting that a bucket can catch, once the water supply is shut off, can wait until morning. Either way, the homeowner can limit the damage right now by turning off the cold water supply to the heater and turning off its power or gas.

The questions that decide tonight or tomorrow

What to tell them while they wait

Say

Find the cold water valve on the pipe going into the top of the heater and turn it off. That stops more water going in.

Not

Just put a towel down for now.

Say

If it is electric, switch off its breaker. If it is gas, turn the gas control to off. Do not stand in water to do either.

Not

Leave it running until the plumber gets there.

Say

If the water is near outlets or the panel, stay out of the water and do not touch anything electrical. I am sending someone tonight.

Not

It can probably wait until morning.

The three ways this goes wrong

A leaking water heater comes down to how much water, from where, and how close to anything electrical. Ask those three things, get the water and the power off, and the calls that need tonight get tonight.

B

I answer the phones for plumbing contractors, and I walk every caller with a leaking water heater through the shutoffs before anyone is booked. callbobai.com