Potterton Boiler No Hot Water: Causes and What to Do

Combi, system or an older regular boiler?

Potterton has made boilers for British homes for decades, so there is a wide spread of ages on London walls. Recent combis and system boilers carry names such as Promax, Titanium, Assure and Gold. Older installations are often heat only boilers, names like Suprima, Profile, Performa and Netaheat, working with a hot water cylinder and a loft tank.

The type decides where the fault is likely to be. On a combi, the hot water is made inside the boiler, so no hot water is a boiler repair. With a cylinder in the airing cupboard, the boiler only heats the water when the controls ask it to, and the fault is often outside the boiler altogether.

E119, E133 and older Potterton lights

Note the exact code before you reset. A reset wipes it, and it is the first thing an engineer needs.

E119 is the code most often seen with no hot water on a modern Potterton. It means the heating system pressure has fallen too low for the boiler to run. With the boiler cold, the gauge should normally read around 1 to 1.5 bar. Top it up through the filling loop as your manual shows and reset once. If it falls again within days, there is a leak or an expansion vessel problem to find.

E133 means the boiler tried to light and did not see a flame. The usual culprits are the gas being off, a prepayment meter out of credit, or a frozen condensate pipe in cold weather. Potterton and Baxi use the same code, and our page on the Baxi E133 fault code covers every cause.

Older Potterton boilers without a display signal faults with lights, or simply do not fire. On those, the checks below and a look at the pilot or burner through the viewing window, if there is one, are the place to start. Do not remove any panel to look.

Checks to make first

All of these are safe and need no tools.

• Pressure: check the gauge with the boiler cold. Heat only boilers on an open vented system have no gauge, which is normal.
• Gas: light a hob to prove the supply.
• Programmer: on a cylinder system, check the hot water channel is on and the clock is right. Potterton branded programmers are common on older systems and often reset after a power cut.
• Cylinder thermostat: the dial strapped to the side of the cylinder should normally be set around 60 degrees. If it has been knocked to minimum, the boiler will not heat the tank.
• Immersion heater: if the cylinder has one, switch it on for an hour. Hot water from it proves the cylinder is fine and the fault is in the boiler or its controls.
• Flow: on a combi, open the tap fully. A trickle may not be enough for the boiler to fire.

Potterton combi: hot radiators, cold taps

If the heating works and the taps do not, the burner, gas and pump are fine. On a Potterton combi the fault is then almost always one of three parts, much the same as on a Baxi, because many Potterton combis share their internal design with Baxi models.

The diverter valve sends heat either to the radiators or to the hot water. Stuck on heating, it gives you exactly this fault. Stuck partly across, it gives warm radiators whenever you run a tap and hot water that never gets properly hot. Our guide to diverter valve replacement cost explains the repair.

The flow sensor tells the boiler you have opened a tap. If it fails, or the flow is restricted by a blocked inlet filter, the boiler stays silent when you run the hot tap but fires normally for the heating.

The plate heat exchanger passes the heat into your tap water and scales up over time in London water. Hot water that fades after a minute, or a boiler that fires and cuts out while the tap runs, points here. Our guide to no hot water from a combi boiler covers the three faults in more depth.

Potterton with a cylinder: heating on, tank cold

On a heat only or system boiler, the demand runs from the programmer to the cylinder thermostat and then to a motorised valve, which opens to the cylinder coil and tells the boiler to fire. If any part of that chain fails, the radiators heat and the cylinder stays cold.

The motorised valve is the most common failure. Its motor burns out or the switch inside the head wears, and on older systems the valve body itself can seize. You can often hear the difference: a healthy valve makes a faint whirr or click when the hot water channel switches on. Our guide to no hot water but the heating works goes through these parts step by step, and if the cylinder itself is the problem, our hot water tank not heating page covers that side.

Is an old Potterton worth repairing?

Often it is. Diverter valves, flow sensors, motorised valves and cylinder thermostats are ordinary parts, and fixing them is usually far cheaper than a new boiler. The answer changes on a very old heat only boiler where parts are hard to get, where the heat exchanger or burner are also in poor shape, or where the boiler keeps failing in different ways. Then it is worth weighing up replacement, and a boiler diagnosis visit gives you the facts to decide on.

Any work inside the case of a gas boiler must be done by a Gas Safe registered engineer. If you smell gas, turn it off at the meter, open the windows and call the gas emergency line on 0800 111 999.

When to call us

Call us on 020 4652 5111 or send an enquiry if a code returns after a reset, if the pressure keeps dropping, if the motorised valve or boiler is dripping, or if the hot water is still cold after the checks above. Give us the boiler name from the front panel, any code, and whether you have a cylinder. We have 20 engineers across London, and our rate is on the pricing page, agreed before anyone attends.