piglet John - can you help?

[cedricsneer]

Or anyone else who knows about plumbing. We are spending the night in our tiny holiday rental flat and we have discovered that although the water to the basin is piping hot, the shower and bath (it's a shower over bath) water is very inconsistent.

We have checked the pressure, which is fine, but when we run the tap (hot and cold going into a mixer for the bath) it comes out lukewarm, goes piping hot and hen quickly settles at lukewarm. It may have always been like this, but as we have only had one (recent) complaint, I kind of doubt it. The shower is tolerably warm, but you really can't run a nice hot bath.

I'm aware this post is becoming epically boring, but we have guests tomorrow and really need to fix it, but I don't even know if it's a boiler problem or a problem with the feed to the bath taps.

Thanks so much for any help - we will probably need a plumber, but I'd love to be able to know what I'm talking about. I'm terrified of being blinded with science and being conned into spending a fortune.

What kind of boiler is there? If you run the hot bath tap, is the water hotter if the tap isn't fully open?

I don't think it makes a difference how far the tap is opened. It's a combi boiler. Thanks!

If you run the bath tap hot only and quite slowly, and at the same time, run the cold water tap in the bathroom sink on full blast, is the water hotter?

With a combi boiler, the amount you open the tap does affect water temperature. More flow means cooler water. Try it. It is worst on bath taps which are bigger than basin taps.

The hot water will also be less hot in winter.

The mixer might also have a thermostatic anti-scald valve, they are normal on shower mixers, less common on baths except in care homes, hospitals etc. Sometimes they have a tiny button to turn past the limiter.

Thank you! It does seem to be a bit hotter when the tap is not fully on - but not as hot as I'd expect. Is there a way around this, or will my guests never get a properly hot bath?

With a combo boiler it is often a long slow process to fill the bath using just the hot tap and adding any cold, if needed, at the end. Have you checked the water temp setting on the boiler? It's possible someone has turned it down.

Also, turn off all the radiatirs, let them go cold. Then run a hot bath. Do any of the radiators start to warm up?