Combi Boiler Pipes Backwards

[glynm15]

Hi all,

I have a combi boiler and its been in the property since we moved in 8 years ago.

12 months ago we had a new bathroom and at the same time changed the kitchen taps. After this the boiler didn't seem to fire up when requesting hot water. It was fine from the bath tap but struggled with the shower and kitchen tap. It progressively got worse. We had British Gas come and look and they changed the diaphragm next to the flow switch. It worked better for about 2 months and has got much worse since.
British Gas came again and this engineer said it it plumped in backwards. The cold pipe going in is actually the hot pipe coming out and vice versa. He said he could changed the pipes around no problem, but then he said it might affect the shower.

Quick questions?

How has the hot water managed to work fine for years if its always been plumbed in backwards?
Do you think it will affect the mixer shower apart from cold being hot etc?
Any other advice appreciated.

Thanks in advance.

 

[jonnyswamp]

Problem with the mixer tap or shower valve rather than crossed pipes I would have thought
The hot and cold water are mixing somewhere and when you turn on a hot tap there isn't enough flow through the boiler to activate the sensor/move the diaphragm and fire it up
Isolate the new kitchen tap then try the hot water, if no different try isolating other mixer taps or showers until you find the one at fault

 

[newcastle phill]

Do you have any reason to doubt his advice.
You can verify if this is the case by referring to the instruction manual and cross referencing the pipes. By switxhing it on and feeling the temperature of the pipes will comfirm correct arrangement

 

[glynm15]

Hi,

Thanks for the replies.

Kitchen tap - can't fire boiler / get hot water.
Bath tap - used too but is now getting worse.
Combination of bath and sink usually gets hot water flowing.

No reason to doubt engineer. It was just that he said, if he did it, it might cause the shower not to work - but he said he's not an expert on them.

 

[Chalked]

+1 for cold back feeding throgh the shower mixer. It will either have non return valve fitted that are sticking open or won't have any!

 

[fubar1000]

I've had some problems with these new style of 'eco / water saving' taps not firing up the boiler when calling / turned on for hot water. Mainly the cheap ones as the flow is restricted. Can be a right pain in the back end

 

[kris]

Hi Glynm ,,,Yeh certain flow rates are so poor they dont activate the flow sensor,
A mixer will always mix water even if back to front just not efficiently as all your doing really is mixing hot n cold, unless its a thermostatic cartridge, stick non return valves under your new taps incase back flow is preventing boiler,

 

[Worcester]

No reason to doubt engineer.

Yes there is, you gave us every reason why you should doubt him.... He works for BG -

They've already been once and their solution (and bill that you paid) hasn't fixed the problem...

Not only that if you didn't doubt him, you wouldn't have come and posted on here, yoyu'd have just paid up. Oh and you would still have the problem...

 

[village idiot]

Yes there is, you gave us every reason why you should doubt him.... He works for BG -

They've already been once and their solution (and bill that you paid) hasn't fixed the problem...

Not only that if you didn't doubt him, you wouldn't have come and posted on here, yoyu'd have just paid up. Oh and you would still have the problem...

Calm down worcester, the OP is just trying to get some help from forum members.

 

[Worcester]

Calm down worcester, the OP is just trying to get some help from forum members.

One of those days, just spent 4 days on our MCS technical audits, so picky on everything at the moment

So just got ansty when he said he trusted the engineer.. Bit like saying "I agree with you, but..."

 

[Allgoode]

Hi,
Sounds like back flow, you should have single check valve on H&C supplies to your mixer type taps. That way you prevent backflow issues and failure of the boiler to sense call/demand for hot water when you turn on the hot tap.
cheers,
Andy

 

[Worcester]

Hi,
Sounds like back flow, you should have single check valve on H&C supplies to your mixer type taps. That way you prevent backflow issues and failure of the boiler to sense call/demand for hot water when you turn on the hot tap.
cheers,
Andy

Hi Andy it will, however if he's got a faulty mixer, then that will still try to back flow, the check valve will stop it, however it will then mean no hot water getting through at all