Boiler fires after the toilet has finished refilling.

[djheath]

I've been putting in a new bathroom and moving some pipes etc. Now everything is connected, when the toilet is flushed and the stop cock in the cistern stops the water filling it, the combi boiler fires up as if a call for hot water has been requested. It stops after about 20-30 seconds. It doesn't happen when the cold tap on the sink is used, which feeds to the toilet.

The only changes to the pipes I have made, apart from moving them around, is to take the cold water feed to the bathroom directly from the main feed from the house supply from under the kitchen sink, where as before, the feed went up into the roof, through a loop where the immersion etc used to be, and then back down to the bathroom. Seemed a bit silly to me to have water going up the house then down. It's an old house so the bathroom is at the back of the kitchen, right next to where the boiler is connected and the water supply to the house.

I assume the sudden pressure change when the cistern stops filling is forcing water through the hot water circuit or something and I need a check valve somewhere.

Can anyone advise what I can do?

Thanks.

 

[djheath]

Ok, i've just done a search, (should have done that before!), and notice people talking about a dead leg which needs bleeding. Well I definitely have a dead leg bit of pipe in the system which is lower than some of the cold water pipes, so that would make sense.

How can I bleed it? Can you get a bleed valve for 15 mm pipe, or should I just get an isolating valve and turn it on until water pours out, then leave it closed?

 

[stardanny]

Best to remove deadleg, up to where it tee off supply pipe.

Daniel.

 

[djheath]

hmm well, I could have done that yesterday, when the ceiling was all down, but today I just boarded it all out and I cannot get to the pipes anymore.

I've just traced in my head where the pipes go and it is as follows. The supply comes into the bathroom, t's off, with one length going to feed the sink and cistern and the other goes up into the ceiling. This then goes to another tee, which comes back into the bathroom and feeds the shower and bath (yet to be plumbed in), and the other side of the tee goes through the old immersion loop then comes back down into the bathroom where I have capped it off. I cant now cap it off where it splits on the second tee since that is hidden in the ceiling.

Is there anything else I can do, other than bleed it?

 

[stardanny]

Either remove deadleg, by remove ceiling where tee is or loose up cap to let air out then tight up. Do the same for bath and shower. It is not ideal to leave deadleg.

Daniel.

 

[Terry lambert]

A non return fitted to the cold main to the boiler should also cure it

 

[gigz]

First thing to do is play around with the stop tap, its probably needs opening more (or closing a bit). Been called out a few times to this, where they've had the water turned off for whatever reason, then when its turned back on the boiler starts firing. If you have' nt created any deadlegs they were already there (although could have been equalised with water). As said it would be better to remove ghem, but not always practical/possible.

 

[srhawksy]

+1 for what terry has said above, is your boiler a ferroli??