Reasons Why Your Hot Water Just Went Cold

Depending on the design of your heating system whether you have an “Open Vented” System or a “Sealed System”, the cause of fault can vary and we highly recommend you arrange for an expert engineer to have a look.

Below we have a list of common faults which might help re-resolve or identify what could be affecting your hot water

Airlocks (Open Vented System)

An airlock is a situation whereby air becomes trapped within the system, which ends up blocking the hot water as it makes its way to your taps or showerheads. An airlock can partially or completely stop hot water flowing out of a tap.

The best way to remove an Airlock is to use mains water pressure from your kitchen sink mixer tap and follow these 3 simple steps.

1 – Use the palm of your hand to block the spout of your kitchen sink tap
2 – Open the hot water tap
3 – Open the cold water tap

The cold water will now flow into the Hot water system and use the pressure to remove the airlock, do this test for between 3-5minutes then release your hand and shut the cold tap, if you have been successful the hot water will start to flow
However, if the issue has not been resolved then we recommend that you call an expert as your system could have underlining pipework issues.

Low Water Pressure

We encounter plenty of phone calls each week regarding hot water issues and low water pressure. Both are linked to the same fault and both can be easily rectified. If your boiler is reading 0 on the pressure gauge and you have no hot water, 9 times out of 10 all you need to do is up the central heating system pressure to between 1 and 2 bar, this can be done by opening the filling loop under your boiler or at your cylinder.

Diverter valves, Pumps 2 Port and 3 Port Valves (Open Vent and Sealed Systems)

These are both common faults with combination boilers and usually go to a fault because of the same reasons, Sludge or a PCB error, you will need to contact your local experts to test this.

Sludge is formed in your heating system due to a lack of maintenance and treatment. Your central heating system should be drained, refilled, and topped up with a central heating inhibitor which will prevent the corrosion process in your heating system. Failure to do so will result in a build-up of sludge which can block up your Diverter valve, 2 port, 3port valve, and your central heating pump.

You can do a manual test using just your hands at home to see one of these components are at fault. We advise that you do not touch or strip down these components nor should you put your hands on any electrical cables.

To test the diverter valve on a combination boiler you can simply turn your central heating off, run the hot water tap out of an outlet and put your hand on the flow pipe coming out of the boiler (usually the far left pipe). If that gets hot while the tap is running, then you know your diverter valve is shut in the wrong position.

The same rule applies for 2 port and 3 Port valves, if you call for hot water or central heating but the valve lever does not move, you can hear the motor has jammed up, or the water is flowing down the wrong pipe or not at all, then you know your valves may need replacing.

Pumps can be tested by a compliant person at home by removing the center eye of the pump using a flat head screwdriver and then sticking a smaller screwdriver in the middle. If the pump is easily stopped or is not moving at all, then this will need replacing.

If a pump feels hotter than usual this is also a sign that the pump is struggling to spin, always consult an expert to check your pump properly.

Other Causes That You Can’t test

Fans, gas valves, NTCs, flow-switches, PCBs, faulty flues, flame sense electrodes, spark electrodes… the list goes on. Boilers are complex machines and there are many components to a central heating system that can cause issues with your hot water and that’s why it takes an experienced heating engineer to work on them.

Intermittent Hot Water or You Want to Learn More? Get Help from The Experts

If you’ve noticed that this keeps happening, then it’s wise to call out a gas safe engineer to try and diagnose the problem. Trying to guess what’s wrong with your boiler yourself could do more harm than good, the information provided above is given as a guide to diagnosing simple faults. We always advise that you call your local experts to professionally diagnose your boiler.

So if you’ve got any problems with your combination boiler, sealed system or open vent system boiler, make sure to give us a call on 0208 323 5678 so that our rapid response team can advise the best course of action.

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