Water Heater Not Heating or Leaking: Repair or Replace?

The two parts that keep it safe

Heating water in a sealed container raises its pressure. Two devices stand between a faulty heater and a dangerous one. The safety cut-out breaks the electrical supply if the thermostat fails and the water overheats. The relief valve opens if the pressure climbs anyway and sends the excess down a small discharge pipe.

Neither should ever be defeated. A relief valve that drips is doing its job or telling you something, and capping its pipe to stop the drip removes the last protection the tank has. A cut-out that has tripped has tripped for a reason, which is why resetting it is a technician's job, done after the cause has been found.

Central and solar systems in villas

Some villas have one large heater serving the whole house, or solar collectors on the roof feeding a tank with an electric back-up. The tank end of those systems has the same parts and fails in the same ways. The difference is access: anything on a roof, and anything with pumps and collectors attached, is a technician's job from the first step, so skip the hands-on checks below and describe the symptoms when you book.

No hot water at all

A heater that produces nothing is usually not getting power, or has stopped using it. The simple causes come first: the wall switch has been turned off, often by a cleaner or a guest, or the breaker for the heater has tripped. In a home where heaters are switched off for the summer, someone may simply not have switched this one back on.

If the switch is on and the breaker is holding, the fault is inside. Either the safety cut-out has opened, or the element has burnt out and no longer heats, or the thermostat has failed in the off position. Our plumbing page lists the thermostat, the element and the supply as the commonest causes of a heater with no hot water, and a simple element or thermostat fault is often put right in the same visit.

Lukewarm water, or hot water that runs out too soon

When a heater that used to manage two showers now manages one, the tank has not shrunk but its useful volume has. Sediment and flakes of scale settle at the bottom and take up space, and a crust of scale on the element slows the transfer of heat into the water, so the tank recovers more slowly between uses.

Before blaming the heater, rule out two ordinary explanations. More people may be using hot water than before. And in winter the water entering the tank is cooler than in summer, so the same heater takes longer and the mixed shower uses more of the hot. If neither applies and the change has been gradual, scale is the likely cause.

Water that is far too hot

Scalding water, steam at the tap, or a relief pipe discharging hot water means the thermostat is no longer switching the element off. This is the fault to take most seriously. The cut-out and the relief valve are there to catch it, but they are a last line, not a way of running the heater. Switch it off at the wall switch, let nobody use the hot taps in that bathroom, and call. Do not turn it back on to see whether it has settled.

Noises, brown water and smells

A rumble, a crackle or a popping sound while the heater is working is water boiling in small pockets under a layer of scale and sediment. It is not dangerous in itself. It does mean the element is working harder than it should, and it is a fair warning that the tank is due for attention.

Brown or rusty water needs one test: does it come from the hot taps only, or from the cold as well? From the hot side only, the rust is coming from inside the heater, which usually means the anode is spent and the lining has failed somewhere. From both, the source is upstream, in the pipes or the storage tank, and that is a different job, covered in our guide to water tank cleaning. A sulphur smell from the hot taps of a heater that has been switched off for weeks usually comes from water that has sat in the tank. Tell the plumber, because the fix involves the tank and the anode and not just running the taps.

The relief valve and its pipe

A few drops from the relief valve's discharge pipe while the tank is heating can be normal. Water expands as it warms, and on many installations the valve releases that small excess. A steady trickle, a drip that continues when the heater has been off for hours, or hot water running from the pipe is not normal. It means the valve is worn or jammed open with scale, or that the pressure or temperature in the tank really is too high.

Either way the answer is a new valve or a repair to whatever is over-pressurising the tank, and both are routine. What must never happen is a cap, a plug or a closed tap on that pipe. If a bucket under the drip fills in a day, that is information for the plumber and a reason to call sooner.

Connections, hoses and valves

The flexible hoses, the isolating valve on the cold inlet, the threaded joints and the gasket where the element is bolted into the tank can all weep. These leaks show as a drip from one fitting, a green or white crust on a joint, or a damp patch directly below a connection. They are repairs, and usually quick ones, provided the water has not been running into the electrical side of the heater.

The tank itself

Water seeping from the casing, rust streaks down the outside, a wet patch that returns after everything has been tightened, or water appearing from the bottom of the jacket with no fitting above it all point to the steel tank. The lining has failed, the steel behind it has corroded, and the hole will grow. There is no patch or sealant for a pressurised tank. The heater has to be replaced.

Until it is, treat it as a leak that can worsen without warning. Switch the heater off, close the valve on its cold inlet, and if you cannot find or turn that valve, close the main stopcock. The first steps for any sudden leak are set out in what to do in the first ten minutes.

When the heater is above a false ceiling

A heater in the ceiling void leaks out of sight. The first sign is often a brown ring on a ceiling tile, a drip through the access panel, or water running out of a light fitting. Do not touch a wet light fitting or its switch. Turn that lighting circuit off at the distribution board as well as the heater, and stay out from under a sagging panel, which can be holding a surprising weight of water.

Once the leak is stopped, the ceiling needs to dry before anyone repairs or repaints it. The order of that work is explained in water stain on the ceiling: what to fix first.

Where to stop

Everything past that list is inside the heater or inside the wiring, and that is where residents get hurt. The terminals behind a heater's cover are live whenever the supply is on, and a wall switch does not prove otherwise if it has been wired wrongly or has failed.

• Do not remove the heater's cover, press the reset button behind it, or adjust the thermostat inside.
• Do not cap, plug, tape or tie off a dripping relief valve or its pipe.
• Do not keep resetting a breaker. Once is a check. More than once is forcing current through a fault.
• Do not open the drain point or try to flush the tank yourself. Scale can stop the drain from closing again, and the water may be hot enough to scald.
• Do not climb into a ceiling void or onto a roof to reach a heater, and do not stand on a bath or a basin to look.
• Do not touch the heater, its pipes or nearby metal fittings if you feel a tingle from a tap or from the water. Switch off at the distribution board and call an electrician at once.

Plumber or electrician?

The heater and everything bolted to it, including its element and thermostat, are dealt with under our plumbing service. The circuit that feeds it is electrical: the breaker, the wall switch, the cable and the earth-leakage protection. If the breaker for the heater trips even when the heater's own switch is off, or the switch is hot, scorched or buzzing, the fault is in the supply and belongs to our electrical service.

You do not need to work out which it is before you call. Describe what happens and in what order, and the right trade is sent. The signs that separate a nuisance trip from a fault are covered in tripping breakers, flickering lights and warm sockets.

The summer switch-off

In summer the water arriving from a roof tank can be warm enough that many households switch their heaters off for months. That is reasonable, and it saves electricity. It also means the first cool week of the year is when faults show up: a thermostat that has stuck, an element that fails on its first long run, a relief valve that drips after a season of sitting still.

If you switch heaters off for the summer, switch them back on one at a time and a few days before you need them, while you are at home and awake. Check each one for hot water, noise and drips over the first day. The same applies after long travel, and switching heaters off before you leave is on the list in our home maintenance calendar.

What maintenance a heater can have

A heater is not a fit-and-forget appliance in hard water. A plumber can drain the sediment, descale or replace the element, test the relief valve and check how much of the anode is left. None of that is a household task, for the reasons given under where to stop. Asking for it before a heater fails costs less than the emergency, and it is when you find out what state the tank is really in.

When a repair makes sense

Repair when the fault is in a single replaceable part, the tank shows no rust or seepage, the hot water runs clear, and the heater has not needed attention recently. Ask the plumber what the inside looked like when the element came out. Light scale and clean steel around the opening are good signs. Thick scale, flaking lining or rusty sludge change the answer even if today's fault is fixed.

When to replace

Replace when the tank leaks, when the hot water runs brown, or when the heater has started to collect faults. Replace, too, when a part is no longer made for that model, or when the repair would mean disturbing fittings so corroded that they are unlikely to seal again. A heater mounted above a finished ceiling deserves less patience than one over a tiled floor with a drain, because the cost of a failure is not the heater. It is the ceiling, the wardrobe below it and sometimes the neighbour's flat.

We do not put a number of years on this. Water quality, how hard the heater works and whether anyone has ever maintained it matter more than its age, and a label date cannot tell you what the tank looks like inside. The same reasoning, applied to washing machines, fridges and ovens, is in repair or replace: a practical rule for appliances.

What to settle before a new heater goes in

A like-for-like swap is simplest, but it is worth checking that the old heater was right in the first place.

• Orientation. A heater built to hang upright must not be fitted on its side, and the reverse. The label states which it is.
• Capacity. Choose by how many people shower one after another, not by what happens to be on the wall now.
• Weight. A litre of water weighs a kilogram, so an 80-litre heater holds 80 kilograms of water before you count the steel. The wall, the brackets or the ceiling frame must be able to carry it.
• A drip tray and a drain beneath any heater mounted above a ceiling, so that a future leak has somewhere to go.
• The relief valve's pipe run to a drain or another safe point, where a discharge will be seen.
• An isolating valve on the cold inlet, so the heater can be shut off without closing the whole home's water.
• The electrical side: a circuit, breaker and switch suited to the new heater's load, with working earth-leakage protection. If the new unit draws more than the old one, that is checked before it is ordered.

If the home is rented

A fixed water heater normally belongs to the property. Who arranges and pays for a repair or a replacement depends on your tenancy contract, so tell your landlord or the managing agent before you approve anything beyond making the heater safe. Mention that the home is rented when you book, because some repairs need the landlord's confirmation first. In a tower, the building may also want to know before water is shut off or work is done in a ceiling void.

On the day

The plumber checks the heater directly and does not assume that the first visible symptom is the cause. A heater that will not heat may have a dead element, or it may simply not be receiving power. Once the fault is identified, the parts and labour are confirmed with you before any repair goes ahead. If the honest answer is that the tank is finished, you hear that before money is spent on parts.

A technician will normally isolate the electrical supply and prove it is off before opening the heater, close the water to it, and drain what has to be drained. After the repair the heater is refilled before the power is restored, because an element switched on in an empty tank burns out in moments. A replacement takes longer than a part swap, since the old unit has to be drained, brought down and taken away.

Before the plumber leaves

Our plumbers run the water with you after a repair, check the joints for drips, and show you any worn part that was replaced. Look at the part. A scaled element or a rod eaten down to its core wire tells you more about what your water is doing to the heater than any explanation. Ask what the inside of the tank looked like and whether the anode was checked.

If the same fault comes back soon afterwards, tell us, so that it is looked at again as the same job and not treated as a new one.

What it costs

A plumbing visit starts from AED 99, which is one plumber and the first hour on site. There is no fixed price for the heater work itself, because a thermostat, an element and a new heater in a ceiling void are very different jobs. Parts and longer work are quoted by the task, from your description and photos or after a free inspection, and the figure is agreed before work begins. No call-out fee is added, and the price is the same on a Friday or a public holiday.

Payment is online by card, from My bookings on this website once the price is confirmed. Every price we quote includes VAT.

Can I keep using the heater until someone comes?

It depends on the fault. A heater that is merely slow or noisy can stay in use. A heater with a slow drip from a joint can be left on if the drip is caught and is nowhere near the wiring, though it is safer switched off. A heater that trips the breaker, overheats the water or leaks from its body should be switched off at the wall and left off. You lose nothing but hot water by switching off, and the cold taps keep working.

Is a dripping relief valve dangerous?

The drip is not. The valve is releasing pressure, which is its purpose. What it may be telling you can matter: a thermostat letting the water get too hot, or pressure in the supply that is higher than the heater likes. A few drops during heating need no action. A constant drip or a flow of hot water needs a plumber, and the pipe must stay open until one arrives.

Why does the heater trip the breaker?

The commonest reason is an element whose metal sheath has cracked. Water reaches the live coil inside, current leaks to earth, and the protective device cuts the power. Damp in the heater's wiring space, from a weeping gasket above it, does the same. Both are found and fixed with the heater isolated and open, which is why the only safe response at home is to leave the breaker off.

Is it worth having an old heater descaled?

If the tank is sound, yes. Clearing sediment and fitting a clean element restores much of the lost capacity and quietens the noise. If the visit shows a spent anode and rust inside, descaling tidies up a tank that is already failing, and the money is better kept for the replacement. The plumber can only tell you which once the heater is open.

Should I switch the heater off when I travel?

Yes. There is no benefit in keeping a tank hot in an empty home, and a heater that develops a fault while nobody is there has weeks to do damage. Switch it off at the wall switch before you leave. If you can, close its inlet valve or the main stopcock as well, so that a failed hose cannot run unnoticed. Turn the water back on before the heater's switch when you return.

Can someone come the same day?

Active leaks are treated as a priority and are often attended the same day, depending on technician availability. A heater that has simply stopped heating is booked for the next convenient slot. We work every day from 8 AM – 8 PM. For a leak, phone +971 52 723 5299 and say that it is an active leak, so the request is seen at once.