Vaillant boiler - hot water for all sinks, Luke warm in bath

[AHolts]

I'm really hoping someone can solve a bit of a mystery for me. We have an ecotec pro 28 combi boiler (6 yrs old) & over the last few months we've noticed that the water for our bath & shower have reduced. It started around September. To be honest I thought maybe I'd knocked the dial to the thermostat by mistake & Would be rectified at the next service.

Last month we had our bathroom refitted (& I mean completely gutted) & whilst doing it, the plumber replaced all the pipe work under the floor boards as was over 20 yrs old. At the same time I asked him if he knew how to turn the water temp up. He checked & confirmed the water temp was already on maximum. When the bathroom was finished unfortunately the water was still not hot, just warm ish. The plumber contacted a boiler engineer to look at the boiler & see what was going on. He thought that a cold pipe was too close to the hot pipe leading to the bath & shower. It sounds plausible, but we always had scaulding hot water for the bath in the past, it got cooler by itself without any changes to pipe layouts. He then said maybe it was the heat exchange, but that doesn't make sense either as both the kitchen & bathroom sink water is still scalding hot.
The following things also make no sense:
- the pipe where the water comes out of the boiler is very hot no matter what tap I use.
- if I run the bathroom sink tap & bath taps at the same time, they are completely different temps.

This may be a red herring, but about a year ago we had a leak from the boiler, which turned out to be a cracked overflow pipe, which was replaced & has now been lagged. Other than servicing, no other work has been done on the boiler.

I'm really hoping someone will have a clue what is going on, my husband is talking about replacing the entire boiler. But given that we don't know 100% that the boiler is the problem, it seems a bit extreme.

All suggestions welcomed.

 

[HERTS P&D]

What happens if you turn the hot bath tap on? does it get hot like the basin?

Andy

 

[mogget]

If the pipe from the boiler is hot, then the water is hot. Logically, this can only mean that heat is being lost from the water somewhere between the boiler and the bath. How strange!

 

[picasso]

Flow rate from the bath might be too fast, dont forget the incoming water is very cold this time of year, was the shower replaced when the pipework was done ?

 

[ALEC1]

mixing valve some where with no non return valves...

 

[Bunnyman]

As Alec said usually shower mixer passing, see if u got isolating valves on the shower pipes, turn em off an try the bath again

 

[AHolts]

We used to have a mixer tap on the bath & to be fair the water pressure wasn't brilliant, although def over 1 bar. We now have the water enter the bath through the pop up waste dial, so unable to test the water pressure.

The water is Luke warm for both the static shower, hand held shower & also the bath. All mixed via a new dial plate. Everything in the bathroom is new, pipes, floor boards, plaster the lot. Although this problem started before the new bathroom. Yet we had 5 years of all being ok and this change happened with no change to anything structurally in the bathroom.

I did wonder if the cold weather would have any effect, but the sink tap is no more than 50cm away from the bath, so surely that would be effected too? I'm baffled.

 

[AHolts]

As Alec said usually shower mixer passing, see if u got isolating valves on the shower pipes, turn em off an try the bath again

Oooo, this is something that's never been mentioned before. Will suggest this to the plumber. Any idea where I might find the valves? Would they be near the boiler, under the bathroom floor, in the mixer dials??? Praying it's not under the floor, as only recently tiled & v expensive to replace.

 

[mogget]

The valves should be in the supply pipes close to the shower valve.

That's where they should be.

 

[AHolts]

Ok, I've just run my hand under the bath water for about 5 minutes. Initially the pressure was good & I could feel the water warming up, feeling like it was getting to a good temp, then after about 30 seconds the heat & pressure dropped off a bit & both fluctuate a bit v warm / Luke warm, good pressure/ poor pressure.

I recall our old taps did this a bit before we replaced them & I just assumed it was cheap taps getting scaled up???

 

[Breesey]

Was the bath tap replaced in the bathroom refit? (I assume it was but you don't actually say)

Is it thermostatic? is it also the control for the shower?

 

[Bunnyman]

Yep that does sound like a thermostatic mixer cartridge playing up on a shower, turn the bath tap down to a low flow say about half does the water start warm then cool off again

 

[AHolts]

Yes, absolutely everything was replaced in the refit.

I've just tried the suggestion of only running the bath on slow. This kept a constant pressure, but the temperature still fluctuated. It never gets as hot as the sink water, but if I could just get the upper temp of the fluctuation I reckon I could get a decent bath.

 

[AHolts]

I have 2 panels. A triple panel with static shower on/off, temp dial & bath on/off. The a double panel which is just hand held shower on/off & temp. All these outlets have low temp water.

 

[Bunnyman]

What do u mean by panels? Is this unit suitable for mains pressure hot water?