New Combi Boilers and Old Toilet...

[Big D]

Good Morning all,

I've just had a new combi boiler put in by those ever so nice British Gas people, however we have one problem with it....

Whenever we flush the toilet it starts to fill up the cistern and when it has finished there is an almighty bang (its more like a VOOMF than a BANG).

It is quite scary for our cats but its also annoying and worrying...

At the moment we have a mini float valve in the cistern, is that up to the job? it is the original valve from when the house was built over 20 years ago?

Can anyone suggest a solution to my problem please.

Regards

Dave

[Andy Hall]

There's your problem right there.

Absolutely. . Is the sound coming from the boiler or the cistern or the pipework?

You've already paid a lot of money for BG to do this (their pricing is generally top of the range), so they should fix it.

.andy

To email, substitute .nospam with .gl

[IMM]

Sounds like a shock arrestor should be installed on the mains pipe.

[Big D]

According to the chap who came round from BG thats whats making the bang, its when the cistern is full and cuts off the water supply, the sudden stop caused the bang.

[IMM]

Get one fitted then.

sell them at about a tenner plus the tee fitting to screw it into.

[John]

Say no more!

Presumably it also pulses when you operate a cold tap elsewhere but you may not have noticed this. One scenario is for the opening of the ball-float valve to create a pressure change within the pipework leading to a travelling wave effect through the boiler which momentarily operates the flow sensor and the boiler tries to start. Things to check would include but not be limited to: All the hot and cold pipes within the house are fully cleared of air with particular attention to the hot pipes. The taps/shower valve/washine machines solenoids are in good condition. None of the appliances contain surge arresters in their hot circuits Your pipes are not excessively long plastic type which can allow surge expansion to travel through the boiler and then recover. Its also worth double checking that your bg pals didn't connect the wc to the hot pipework!