Combi boiler shower

mickflynn39

I recently had a Vaillant Ecotec 837 boiler installed. I went for the most powerful boiler I could to give me a decent 'powerful' shower. The boiler is capable of giving 15.2 litres per minute of domestic hot water through a 35 degree temperature rise. I could have gone for the smaller 831 boiler as this was more than powerful enough to heat the house but would have given 12.7 litres per minute. Given that I've got 20 litres per minute coming into the house with 3 bar of pressure, I would have expected 15.2 litres per minute on my domestic hot water. I'm getting nowhere near that.

I have a Bathstore Metro thermostatic concealed bath/shower mixer which controls the water to the shower and the bath. I've been very disappointed with the power of the shower. I've measured the flow rate from the shower and it is only 7.4 litres per minute.

I got Yorkshire Water out and they checked my water pressure and flow rate. At the outside tap it was 3 bar and 20 litres per minute. I then checked all the taps and outlets in the house and found the following. Kitchen sink - cold 14.0 and hot 9.7. Bathroom basin - cold 10.2 and hot 8.4. Bath - cold 14.0 and hot 9.7. Shower (without shower head on) - cold 12.4 and hot 9.2. Shower - mixed hot and cold 7.4.

The kitchen sink is actually closer to where the mains water enters the property so I was surprised that the flow rate dropped so much from 20 to 14 litres per min. I have a monoblock sink mixer which has 15mm pipe from the mains reducing down to 12mm where the pipe meets the mixer. This obviously slows the flow rate down but even so I didn't expect such a huge reduction.

The bathroom basin cold is only 10.2. Again this is a monoblock mixer and is further away from the mains inlet. There is also an inline isolating valve which isn't full bore. So I'm assuming that the inline isolating valve has further slowed down the flow rate which is why the flow rate is lower than through the kitchen sink.

The bath cold is 14 and this goes through the bath/shower mixer and enters the bath through a spout. There are no inline isolating valves so the only think slowing down the flow rate is the length of pipe from the mains and the bath/shower mixer. I would have expected the bath cold flow rate to be higher given the 20 litres per minute coming into the property.

The hot figures as previously mentioned also seem to be on the low side. There is an isolating valve that is not full bore in the pipework for the hot before the water reaches any of the hot outlets. This will obviously slow the flow rate down but the drop still seems huge.

I know the pipework and boiler and outlets will all have an impact on flow rate but I just didn't think it would be so huge.

My daughter has just bought a new house with a less powerful boiler and she says her shower is much more powerful than mine so there is something that is not quite right. My shower is not much better than an electric shower.

I intend to change the isolator valve in the hot pipework to a full bore one but other than this I can't think of anything else to improve the situation.

Is what I'm getting reasonable or maybe the shower valve needs looking at?

Any advice would be appreciated as at the moment I feel I've wasted a lot of money getting a high spec powerful boiler for no good reason.