Shower hot water flow problem

[SimonBea]

My wife and I moved into our first house back in October. A couple of months later the shower gave up. This was a fairly old looking mira event power shower so has hot and cold feeds. I bought a new mira power shower for a quick swap and here the problems started.

On cold the shower works as it should, when turning it onto the hot for the first minute or two the shower struggles to pump out anything at a constant flow with it stuttering. After this you get a few minutes where the shower works as it should, that's fine for me but the wife isn't quite as quick and so suffers when the it goes back to wavering amounts of flow from the shower.

When we first had the problems I took the shower of the wall to check the feeds, I put a couple of tanks of water through the hot to see if there were any air locks but this didn't change anything. I also had two different plumbers over for some advice. The first raised the vent pipe but this didn't change anything. The other could only suggest that on the hot water feed valve we don't open it fully so it gives a more constant flow albeit restricted. The only other suggestion has been to raise the water tank in the loft, this is a coffin style tank so plenty of scope for this.

Before I embark on this which I hope would be a solution does anybody else have any suggestions?

Our system is on a fire back boiler with the hot water cylinder on the ground floor and water tank in the loft, feeds to the shower come from the loft.

Many thanks

 

[Spikey101]

This is a bit of an odd one. Did the old shower work ok before it broke?

These showers are designed to work on extremely low pressure systems so raising the tank might work but it shouldn't need to be. It literally sucks water from the tanks. I doubt it would be sucking it air although this is a possibility. If there was a constant flow of hot water when you took it direct from the feed you should be ok. The stuttering could be due to a faulty isolation valve restricting the flow too much, or possibly a bad non-return valve? I'm guessing these units have one inside them somewhere although I haven't worked on one.

If the old shower didn't stutter and this new one is the same specs, and you are getting a fine flow from the hot water feed to the shower then everything points to a fault inside the unit. Make sure the pump is bled properly also, I doubt it is this but there might be a bleed screw inside the unit to check.

 

[SimonBea]

As far as I am aware the shower was ok before - this is what stumped the plumbers we had over. It was very loud but I put this down to it being an old unit. I don't recall any issues regards to flow when on hot.

In terms of it being same specs, I am not sure on this, it was an old Mira 'Event' from memory but I am not sure how this compares with a regards to flow rate etc.

Just to be clear, the hot feed splutters without the shower on the wall so I believe the problem is the plumbing rather than the unit.

Thanks for the reply

 

[longdogs]

As far as I am aware the shower was ok before - this is what stumped the plumbers we had over. It was very loud but I put this down to it being an old unit. I don't recall any issues regards to flow when on hot.

In terms of it being same specs, I am not sure on this, it was an old Mira 'Event' from memory but I am not sure how this compares with a regards to flow rate etc.

Just to be clear, the hot feed splutters without the shower on the wall so I believe the problem is the plumbing rather than the unit.

Thanks for the reply

Was the cold water tank drained to fit the new shower? Air or debris could be trapped in the pipe. Have you tried connecting a hose from a mains fed tap to the hot shower feed?

Has the new shower been fitted slightly higher than the old one?

 

[SimonBea]

Water tank wasn't drained no. Just turned the restrictor valves for the hot and cold feeds to the shower which are located in the loft.

Shower is fitted in exactly the same place.

Sorry my plumbing skills are...zero, what would connecting a hose from the mains feed to the hot shower feed do?

Thanks

 

[SimonBea]

What also baffles me is how we can get a 3/4 minute window where it works perfectly and then is struggles before and after this

 

[SimonBea]

Just to close this, this weekend we raised the tank by approx. 60cm and this morning the shower was at full strength! Lucky because we had run out of other options!

 

[longdogs]

Just to close this, this weekend we raised the tank by approx. 60cm and this morning the shower was at full strength! Lucky because we had run out of other options!

Sorry I have only just got back to see your questions but glad you got it sorted.