Cold water at hot taps.

[surge2k1]

I have a baxi 105e combi boiler. I had a problem whereby the boiler would not fire to heat the hot water. An engineer came and replaced the diaphragm and it now fires as it should. He also rteplaced the scaled up DHW switch.

The outlet pipe from the boiler is hot but by the time it reaches the taps it is cold. I have hot water intermittently, particularly at the kitchen tap which is next to the boiler and some upstairs from the bathroom sink. I had a bit of hot water from the bath but none from the shower.

It appears that the further away from the boiler I get and the higher the water flow then the temperature is less and the less time any heat lasts.

 

[plumberdan]

that boiler is a piece of cheap s*it, worth nothing but scrap, cant handle high flow rate through boiler, just cant heat the water up fast enough, some have a go hero(6month plumber/gas man) fitted it in my private rented house, cheap as chips! try reducing the isolation valve on the cold mains to boiler while running a tap probably best with bath and keep reducing till the pipe gets lovely and hot, had to do it with mine.

 

[surge2k1]

Cheers for that, will give it a go. It was working frine prior to the firing problem though. We came into the flat on 16th December and has worked fine up till about 19th Jan.

Had an engineer out who thinks its back pressure to the hot circuit, however if the cold water and hot water circuits do not meet till the mixer taps then surely the cold water cant mix before then. This also doesnt explain why it is hot to begin with (apart from the shower).

 

[plumberdan]

the pressures are both mains so should be relativley the same so back pressure even with a mixer tap that mixes within the body of the tap is unlikley, the mains cold isolation valve on boiler may have been adjusted after install then when the bloke came to repair he shut it to change parts and just opened it fully once he'd finished, just might need the fine adjusment again.

 

[picasso]

Make sure both the meter control lever and the boiler gas tap are turned fully on, are the kitchen taps monoblock ? if they are you may need a check valve on the hot or it could be the cold water passing into the hot somewhere else.

 

[plumberdan]

how is it going to back feed its the same pressure just different flow rates. the tap also should mix at the spout not within the body so it cant back flow

 

[picasso]

A monoblock kitchen tap that needs a check valve

http://www.homesupply.co.uk/bristan_java_single_flow_monobloc_sink_mixer=JSFSNKC.htm

a typical plate heat exchanger has enough resistance to make backfeed from the cold main possible.

 

[plumberdan]

thats for low pressure

 

[plumberdan]

look at the medium and high pressure taps, didnt see any with check valves required, only looked at 10.

 

[plumberdan]

And if it is the tap why wasnt it doing it before the engineer fixed the boiler???

 

[picasso]

http://www.burgeandgunson.co.uk/Kitchen_systems/kitchen_blanco_mixer_taps.html

high pressure taps with check valves

I am not saying its the tap, what I am saying is that check valves can stick open and cause mixing/backflow, a lot more common on showers but can happen on monobloc taps.

 

[plumberdan]

okay fair enough, but just after boiler got fixed??? what do you think about the boiler cold main isolation valve and the water flowing to fast for boiler picasso?

 

[picasso]

okay fair enough, but just after boiler got fixed??? what do you think about the boiler cold main isolation valve and the water flowing to fast for boiler picasso?

no idea, need a bit more info from the op.

 

[surge2k1]

What info would u like? I thought about the inlet valve but if the hot water outlet is getting very hot, then does this not mean that the boiler is succesfully heating the volume of water which is passing through? It remains hot when the taps are opened aswell. p.s. the boiler is actually a baxi 80 HE not 105e.