Hot taps run cold - not the boiler, I reckon...

[plumb-line]

Hi,

My cousin just bought a place; last Friday of Feb 09. The bathroom was a big selling point. It had been redone only two years back and finished with fancy slate stone tiles on the walls, downlights, sunken floor, the whole bit, including a new Worcester-Bosch 28i Junior combi boiler which has been fitted in the bathroom (upstairs). Every tap in the house is a mixer tap. The bathroom taps are quite fancy. You have one left/right "flow control" toggle for the bath, one left/right "flow control" toggle for the shower, and in between those two you have a third that is shared and dictates what the temperature both will be delievered at (flow control = the amount of water allowed out the tap / unit of time). This third temperature control is marked such that it suggests it guages the temperature of the hot and cold water supplies and mixes them to provide you with the temperature you have set on the control. If you turn the control to the far left (hot) you get to 50, and if you go to the far right (cold) you get 25 with the mid-point being 38, or something like that. All the other taps are regular single handle mixers. Only the kitchen taps allow for easy access to their supply pipes, etc. The bath and bath sink taps have been sealed into either the wall (not boxing, i.e. a cavity in the wall that has been tiled over) or the tiled boxing (with no capped screws visible suggesting you have to break it all down to get inside). It looks lovely, mind you.

The first few days everything was going swimmingly. Hot water was flowing out of every tap with tremendous force. Oh yes, they have fantastic pressure, 2.5 bars of it in fact, according to the W-B 28i Junior. Then, come Tuesday, the shower began to "fail". Turn the heat right up, and it would only send out sub-lukewarm water. The bathroom sink and downstairs kitchen hot water was fine at this stage. However, a day or two on everything went.

Now here's the weird thing. Apart from the bath and shower, the other two will run hot water for a few seconds and then turn cold; the bath and shower are cold from the off, ALWAYS. The boiler always kicks in though, and the hot water outlet pipe is so hot you can't hold it. It cannot be the boiler. If you run all the hot taps simultaneously the downstairs kitchen taps get hot, very hot. I have the idea that one of the mixers is allowing the cold water to get into the hot water pipe work, as if the mixer system is forming some kind of bridge. Does this make any sense?

Like I say, the boiler is definitely kicking out hot water. You can feel the CH hot water and general hot water supplies coming out the boiler are SUPER hot. The shower/bath with their fancy thermostat are always cold, no matter what you do, but the other two start off warm and turn cold, and if you have all hot taps running simultaneuously you get hot water downstairs in the kitchen. Any ideas? This is driving us nuts!!! We would like to test the theory by turning off the cold supply at the individual taps, but there is no access so far as we can tell, and we don't want to go ripping up a pretty bathroom over a hunch.

TIA.

 

[buffy27]

i read through this twice .nothing logical jumping out to me as a solution.problem being the issues don t add up to logic.sounds like pipe work mixed up , which can be disasterous as it seems to be in your case.really can t make sence of it.get a plumber in.give details of the area and c if one of the clever boys on here can get to u . good details etc in the post but its one of those jobs that needs to be looked at in the flesh. best of luck. p s where in uk are u .

 

[daved]

Have you got a combimate in your cold water feeding the boiler? If so has the sylphos balls been changed recently? If not changed regularly they can break up and pass through into the heat exchanger thus restricting the flow. Can you get hot water by turning down the flow on the rising main? (Just for testing) Or will the taps run hot if you set the taps on a slow flow. I'm speaking from a recent experiance here. My Bath taps would run cold but basin and kitchen were fine. I presume because the flow from Bath taps being greater. Eventually cleared itself after I changed the said sylphos balls.

 

[Marcopolo]

When you mentioned " a bridge" I think you were on the right track it sounds like cold mains is trying to push back down the hot through one of the previously mentioned mixers, check for sudden temp changes on the mixer inlet pipes when the problem occurs then fit non returns on the offending mixer. Intrested to see if this solves the problem.

 

[plumb-line]

Hi all,

Found the problem a couple of weeks back. It turned out to be the thermostat for the bath / shower. We managed to get hold of the plumber who fitted the bathroom and he sussed it pretty quick. There was some valved that needed replacing, and in his experience they tend to go every two to three years. When this non-return valve goes it allows the cold water to flow through in to the hot water supply and overpowers it. That's why the bath / shower was worst hit because that's the tap that had this fancy thermostat fitted to its workings. Silly design, but its expensive to downgrade it and now that I know about it, and got a couple of free spares of the supplier, I should be good for the next four years or so.

Thanks for all your input.

Regards.