Here at EPM, we get our fair share of calls that start like this:

“My hot water’s gone cold overnight.”
“The cylinder’s warm, but the water isn’t hot.”
“The boost used to work — now nothing’s happening.”

Sound familiar? If you rely on your immersion heater — either as a backup to your boiler, or your main source of hot water — it’s important to know the early warning signs that it’s failing.

Here are the 5 most common signs your immersion heater might be on its last legs — and what you can do about it.

1️.You're Not Getting Any Hot Water (Or It’s Inconsistent)

If your immersion heater used to heat water just fine, but now you're getting:

• No hot water at all

• Hot water only sometimes

• Or water that runs hot, then goes cold quickly...

…it’s often a sign that the heating element is failing or completely burnt out.

 Tip: Try the boost switch manually if you have one. If the water still doesn’t heat, it's time to call in a professional.

2️. The Immersion Heater Is Tripping the Fuse or Breaker

This is a red flag. If every time the immersion heater kicks in, it trips the circuit:

🔧 It’s likely the element is damaged or shorting inside the tank — which can also indicate limescale buildup around it (though that’s rare here in Exeter, where the water’s fairly soft).

Don’t keep resetting it. It could be a safety issue, and needs checking by a qualified electrician.

3️. It's Taking Way Too Long to Heat Up

A healthy immersion heater should warm up a full cylinder of water in 1–2 hours, depending on the size.

If it’s suddenly taking much longer than usual, it may be:

• An ageing heating element struggling to keep up

• Faulty wiring or a loose connection

• A thermostat that’s lost its accuracy

We can test all of these quickly during a visit.

4️. You Hear Popping or Hissing Sounds

Some low-level noise can be normal, especially as water heats — but loud popping, hissing, or bubbling often means the element is overheating or surrounded by air pockets.

It’s not always dangerous, but it’s a clear sign something isn’t right — and efficiency will drop as a result.

5️. Your Energy Bills Are Creeping Up

If your immersion heater’s running inefficiently (or constantly kicking in because your boiler isn’t working properly), you might notice your electricity usage climbing.

It’s a subtle sign — but worth checking if you’ve ruled out other causes.

A newer, more efficient immersion setup — or better yet, addressing the root cause — can save money in the long run.

Can You Just Replace the Element?

Sometimes, yes. If the tank is in good condition, and it’s just the element that’s failed, we can usually swap it out — quickly and affordably.

But if your cylinder is very old, corroded, or if there are repeated issues, it might be more cost-effective to upgrade the whole hot water system.

We’ll always give honest advice, based on what’s best for your home.

Final Word from EPM

An immersion heater isn’t something most people think about — until it stops working. But if you spot the signs early, you can avoid a cold shower (or a costly breakdown).

Whether you need a simple repair or a full hot water upgrade, we’re here to help across Exeter and Devon.

Need us to check yours? Complete an online form— or give us a ring for free, no-pressure advice.