Water rushes to radiators when toilet is refilling

[sundaybighouse]

I just got a new combi boiler (Worcester Bosch Greenstar 30CDi) installed. It replaced a conventional boiler plus water tank. The boiler is located in the eaves of the loft. The loft has been converted to 2 bedrooms and a bathroom.

When the upstairs toilet is refilling there is a really loud noise of what sounds like water rushing to the radiator valves. This didn't happen with the old boiler.

I don't understand how flushing the toilet can cause water to be sent to the radiator?

Does anyone have any idea what is causing this?

Thanks

 

[Andygasman2010]

Maybe it has been piped up wrong. What does your installer say?

 

[sundaybighouse]

Yeah that's what I'm afraid of. He's coming back on Tuesday to fit the downstairs bathroom radiator (bathroom is getting redorated so that's why rad wasn't installed with others). When I phoned him he said oh there's no pipes near the bedroom radiators so it shouldn't be happening, then said something about the TRV. It's clearly not that though, I can feel the water going through the pipes to the rad when the toilet refills.

In what way could he have messed up the piping?

 

[Andygasman2010]

I can't imagine why you'd have the fault you do. Post back when he tells you what the problem is.

 

[sundaybighouse]

I will do.

 

[Morris40]

do the affected radiators get hot when heating goes on ?

 

[joinerjohn]

Does your toilet fill with hot water ??

 

[sundaybighouse]

Hi yeah the rad does get hot.

It appears the cold water feed from the boiler goes to a t piece, the left pipe goes to the radiator the right goes to the toilet and shower, does this sound normal?

 

[sundaybighouse]

It fills with cold.

 

[sundaybighouse]

As far as I can make out it looks like this, sorry about bad drawing.

Why would the cold be going to my rads?

View media item 31065

 

[Morris40]

the cold feed goes into the boiler and T's off to the toilet and taps before it gets to the boiler, the hot comes from the boiler and goes off to all the hot outlets, the flow and return from the boiler for the heating will come out of the boiler in 22mm and only go to the rads, depending on the boiler there will be a filling loop somewhere ( different place on a valliant to a worcester bosch ) but basically it connects the cold in to the boiler to the flow/return for the heating so you can top up the heating system, will have a tap at both ends to turn on and off

 

[sundaybighouse]

Thanks for explaining morris, do you have any idea why I hear the rushing noise of water to the radiator when the toilet refills?

 

[Morris40]

nope, all i can say is it shouldn't, sorry but you'll have to get your installer to take a look, does your pressure gauge on the boiler remain steady when this happens ?

 

[mickyg]

a dead leg would cause the boiler to fire, but not through the heating, most bizarre.

 

[sundaybighouse]

Yes, it remains at just above 1 bar.

Ok I'll speak to installer and post the result.