Electric shower takes while to cool

[Crossfingers]

I have a strange problem with my Mira Sport electric shower. When I first turn it on its hot, even at the coldest setting. I have to let it run for a while, hear a thunk from the pipes under the floorboards and the cooler water comes with a bit more pressure. Seems toe it's not full pressure at first and what is there gets all the heat. It didn't always do this. I have a pressure reducing valve to reduce to 3 bar and a water softener (if they make a difference)

Any advice?

Thanks

 

[fowlerboi]

Do you flush the toilet before jumping in the shower?

 

[Crossfingers]

Do you flush the toilet before jumping in the shower?

Not always, but doesn't make a difference that I can tell.

 

[fowlerboi]

If your toilet was refilling it may take some pressure away from your shower if your pressure isn't very good, and toilets can also cause water hammer which is the bang

The Mira Azora electric shower says to not fit check valves on the inlet to prevent pressure build up. I see nothing of that in the sport instructions.

Is it just happening in the warmer weather? It could be that the incoming mains is a bit hot and the shower is struggling to not heat it, the flow restrictor finds an equilibrium which and then its fine. I have it with mine occasionally you need to turn the temp down a little and then back up to get the shower going. Try turning the temperature mode down. The sport instructions suggest this.

 

[Crossfingers]

It always happens a bit in hit weather I can notice that the coldest setting doesn't get cold cold.
When I start it I turn it to coldest and still have to wait. Didn't always have this problem, I think it might have started when the reducing valve was fitted. It's set to 3 bar as that's what the softener says, our water pressure is a lot higher

I just googled water hammer and it says it can be fixed by draining the system, I might try that.

Thanks for the advice

 

[fowlerboi]

not sure what you read but you can't cure water hammer by draining it.

Although you've turned it down have you changed the top section down to low?

 

[Crossfingers]

not sure what you read but you can't cure water hammer by draining it.

Although you've turned it down have you changed the top section down to low?

It didn't mean a full drain, just turn off the mains and let the tap run empty

On low power it's controls the water temp, at high it doesn't but no difference in pressure. When the hammer happens there's no noticeable change in pressure, just a jolt in the water coming out but the temp is more controllable at high power.

 

[John.g]

The jolt, possibly something to do with the PRV being fully shut until the shower solenoid valve opens instantly?. If the cold feed and any hot pipework run side by side then the shower can run very hot until the pipe temperature falls to the mains temperature, it normally takes ~ 15 to 20 seconds to attain normal showering temperature. I had a Mira Sport for over 18 years but fed directly from the mains at 2.8/3.5 bar, I run off a few litres of water from the bathroom basin cold tap which is mains fed if I am first in the shower in the morning.