Shower Water Temperature

[ECMOR]

We have a shower where the water comes from the taps for the bath through a metal pipe - photo attached (apologies for the fact it needs a clean).

The mixing has always been fine and temperature easily adjustable and stays at the temp we've mixed it to be.

However, about 2 weeks ago my housemate managed to break the shower head, so I bought a new one and attached it to the hose, no problem - or so I thought!

Ever since then the water will not mix properly, it's either freezing cold or scalding hot and only about 5 seconds of usable temp water every 2 minutes or so as you have to continually adjust the taps.

We've contacted our landlord but they've not replied, any one have any thoughts in the meantime?!

Not helpful but I'm watching for answers as I have exactly the same problem with a fixed shower

#PagingPigletJohn - he'll know..

you've got a combi boiler, haven't you.

Take the shower head off and let the water run out of the end of the hose. Can you control the temperature better?

Mine isn't a combi It's a system boiler with a megaflow I don't get it at all.. I've noticed with mine that the height you hold the handset at makes a difference. Mix the water with the handset low & all fine, but lift it above your head & it goes cold. Sorry to highjack the thread!

Thanks @PigletJohn - I'll check if that's the case when I get home.
If that temperature is normal when the shower head is off, what's the fix?

bigger head.

The head I replaced it with is bigger than the original was and one of the bigger sizes I've seen, but willing to give it a go - do you think there are any other solutions before I try?

have you tried the naked hose yet?

Yes just tried it and the water mixes fine just with the hose!

This sometimes happen with a combi boiler.

The boiler varies its power output (for example between 8kW and 30kW)

If you run a bath tap, there may be so much water passing through the boiler (the rate of flow) that the boiler, even at full power, is unable to make it fully hot, especially in winter when the incoming water is very cold. On the other hand, when not much water is flowing, then the boiler, even when fully modulated down, may raise it to a temperature that is scalding hot, and will then turn the flame off for safety. This happens more in summer when the incoming supply is a bit warmer.

In your case, the flow may have been reduced if the newer shower head has smaller holes and allows insufficient water out.

It can also happen if flow is obstructed by scale or sediment in the boiler, or if you are in a rural area with a poor water supply, or an old house with narrow pipes, or if there is a plumbing error such as narrow service valves, or someone has turned a stopcock down to reduce noise or save water. Or if you have flashy stylish Italian taps with narrow waterways.

You can experiment by filling a bucket at the kitchen cold tap, the bath tap, and the shower hot, timing it, and calculating litres per minute. 12 litres per minute is about as much as most combis can deliver.

@JellyPeanut

Start a new thread please. Your installation is different, so the cause and the possible remedy will be different. Having two different questions in one thread will be confusing.