The boiler pressure kept climbing, even with the boiler switched off, and the customer had been bleeding water out of the radiators to bring it down. We found a pinholed plate heat exchanger, had one on the van, and replaced it along with the pressure relief valve on the same visit. The customer had been expecting to need a new boiler.
A customer in Great Barr had a Potterton Gold combi whose pressure kept going up. They had been bleeding water out of the radiators to bring it down, only to find it climbing again, even with the boiler switched off. We diagnosed a pinholed plate heat exchanger. We had the part on the van, so we replaced it there and then, and replaced the pressure relief valve on the same visit. The customer had been expecting to be told they needed a new boiler, and was extremely happy to keep the one they had.
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£99 in office hours (Mon–Fri, 8am–5.30pm) covers attendance, diagnosis and the first hour. Parts and any further work are quoted and agreed before we carry on. Out of hours, the price is quoted by phone before we set off.
No travel charge within 10 miles of B20 2JS. Further out, £2 per mile may apply — always agreed before anything is booked. Full price list
Smell gas now? Do not use this form or wait for a reply. Call the National Gas Emergency Service free on 0800 111 999 (24 hours). If you are using a mobile, make the call from outside. Open doors and windows, do not switch electrics on or off, do not smoke or use naked flames, and turn the gas off at the meter if it is safe to do so, unless the meter is in a cellar or basement. Once the supply has been made safe, we can trace and repair the fault.
The customer in Great Barr had a Potterton Gold combi, and the pressure on the gauge kept rising. They had been bleeding water out of the radiators to bring it down, but it went straight back up, even with the boiler switched off.
Pressure that climbs with the boiler off means water is getting into the heating circuit from somewhere. We diagnosed a pinholed plate heat exchanger. That is the part that heats the tap water: mains water runs through one side of it and heating water through the other, and a pinhole between the two lets the higher-pressure mains water push into the heating. The third photo is the plate heat exchanger out of the boiler.
We had a plate heat exchanger for this boiler on the van, so we replaced it on the same visit. We also replaced the pressure relief valve, the safety valve that lets water out if the pressure goes too high. Our Potterton boiler repair page covers other Potterton faults.
The customer had been expecting to be told they needed a new boiler. They didn't: one part, fitted on the first visit, and they were extremely happy to keep the boiler they had.
In office hours (Mon–Fri 8am–5.30pm) a boiler repair is £99, covering attendance, diagnosis and the first hour, with parts quoted and agreed before we fit them. Out of hours we quote the price on the phone before we set off. Details are on our price list.
On a combi boiler, a common cause is a leak inside the plate heat exchanger, the part that heats your tap water. Mains water is at a higher pressure than the heating, so a pinhole lets it push through into the heating circuit and the pressure climbs. A filling loop left open or letting by can do the same. It needs an engineer to find which.
It only helps for a while, because the water keeps coming back in. Get the cause found. If the pressure gauge is in the red, switch the boiler off and call an engineer.
A safety valve that opens and lets water out of the heating system if the pressure goes too high. We replaced it on this boiler at the same visit.
Not necessarily. Here it was one part, the plate heat exchanger, and the boiler was repaired on the same visit.
In office hours (Mon–Fri 8am–5.30pm) a boiler repair is £99, covering attendance, diagnosis and the first hour, with parts quoted and agreed before we fit them.
Job attended and photographed by our engineers, October 2026. Written up by Saeed Iqbal, the engineer who leads Synergy Gas & Plumbing (Gas Safe registered 594385). More of our work in the area is on our Great Barr page, and every job we write up is on the case studies index.
£99 diagnosis + first hour
£99 in office hours (Mon–Fri, 8am–5.30pm) covers attendance, diagnosis and the first hour. Parts and any further work are quoted and agreed before we carry on. Out of hours, the price is quoted by phone before we set off.
No travel charge within 10 miles of B20 2JS. Further out, £2 per mile may apply — always agreed before anything is booked.
No heating or hot water and E133 on the display. The condensate trap was blocked with sludge; we cleared it and had the boiler running again, with a service booked for the following week.
Read the case studyOverheat light flashing and low pressure. We topped it up, tightened a loose automatic air vent that started leaking, and tested the heating.
Read the case studyThe diverter valve was packed with sludge and came off the van on the first visit. The plate heat exchanger behind it was blocked too, so it was ordered and fitted on a return visit. Landlord and tenant both sorted.
Read the case study£99 in office hours covers attendance, diagnosis and the first hour. Parts quoted before we fetch them.
