Erratic hot water

[annavc]

For the last couple of weeks the hot water from a combi-boiler has been really erratic. Sometimes it works fine, other times we have none and can only get it to work if we turn the heating on. The landlord had a boiler engineer to look at it today but inevitably it chose that time to work perfectly and he couldn't find anything wrong with it. He suggested calling Thames Water to see if there were works going on in the area or if there were known pressure problems but they say there is nothing that should be affecting it so we're now at a bit of a loss! Any bright ideas about what could be causing it and what can be done to resolve it would be very welcome. TIA.

[gluteusmaxi]

Hi. I am not an expert but we had a similar problem. We have a megaflow system though. This is how our plumber fixed it. He turned the main water supply off and then turned the lowest hot tap on until the water stopped coming out. He then turned the mains back on, let the tap run for a while and then turn the tap off. It fixed our problem. There was an airlock in the system. Have you tried bleeding the radiators? You must do it with the heating turned off. Just a thought which may help you without having to pay to call someone out , again. Good luck, and if this doesn't fix the problem I guess you will have to go back to your landlord.

[annavc]

Thanks gluteusmaxi, I'll try what you suggest and see if it works.

[gasman]

It sounds like a classic diverter valve problem. Starting off a bit erratic and hit n miss. It will get worse untill you have no hot water at all and evenually no heating aswell. Any heating engineer should recognise these symtoms and it is simply a matter of good servicing and replacing the diverter's diaphragm every three years. If you're appliance has not been regulary serviced or had its diaphragm changed in the last three years then it it time for a full service including changing the diaphragm. Most landlords just have the mandatory gas safety tests performed once a year to satisfy their legal obligation, But very rarley have them fully serviced....To sum it up a new diagphragm and a service will sort out the problem.

[annavc]

Thanks gasman. I've told the landlord what you said and he seemed to think it might be a possibility so is getting another engineer in next week to replace the diaphram and service the boiler. Hopefully it will fix the problem.

[gasman]

Hi annavc, Just wondering if you got it sorted ???

[annavc]

Hi gasman. Yes, it is sorted thank you. The landlord brought a new engineer out who changed the diaphram and also something else which had apparently corroded (can't remember what it was called!). It is now working fine and we have constant hot water again! Thank you very much for your advice.