Low Pressure in Shower head with a new combi

barat378

Hi

I'm new here so hoping someone can help, would really appreciate some advice!

We've just had our old boiler system (system boiler with hot water tank) removed and had a combi boiler installed. The plumber recommended a min of 34cdi Worcester Bosch, so i went one higher to a 38CDi.
We have 3 toilets, 2 showers, 11 radiators (4 bed detached 2001 build). Water pressure in all basin taps and bath taps is strong (cold and hot) - no problems there. The showers run on the combi system (with a thermostat, not mixer) however the pressure is very low compared to the taps. The showers are both ceiling mounted (rain showers) - does the size of the house play a part in this? How can we increase the pressure to the showers, as the taps are absolutely fine (strong). Would really like stronger pressure in the showers :-(

The other thing is if there is chance to increase the pressure by adding an additional pump ? i wonder ? this is something i dont know.

Thank you in advance for your help.
Barat

Owain_Moneysaver

Even a 38kW combi will be limited in flow, especially in winter, but if you find it okay for a bath then most showers should be okay. It's possible that your rain showers just aren't suited for combi operation. Some thermostatic showers also don't play nicely with combis as the thermostat and the combi temperature regulators fight each other.

You can't pump from a combi boiler output so that isn't an option.

EachPenny

barat378 wrote: »

Water pressure in all basin taps and bath taps is strong (cold and hot) - no problems there. The showers run on the combi system (with a thermostat, not mixer) however the pressure is very low compared to the taps.

Are the showers supplied by the same pipework that supplies the taps, or are they run separately? With gravity systems (hot water tank) it was usual practice to have separate supply pipework for the shower(s) so that someone turning on a tap elsewhere in the house wouldn't cause a sudden temperature change.

I'm thinking it is possible that the plumber/assistant might have turned a valve off during the installation work and didn't put it back on fully when they finished?

Typhoon2000

I feel you should have stuck with a system boiler and unvented hot water tank if you want main pressure hot water or heating and hot water at the same time. Bathroom taps are usually low flow to conserve water ( you can’t really tell what the pressure is because the same amount of water comes out regardless). You would need a lot more water for a rainfall shower than a bathroom tap could provide.
You find it’s better in the summer when the incoming mains water is not as cold.

Norman_Castle

The rain showers are possibly the problem. Try replacing one with a standard shower head.

fezster

The 38CDi Combi Boiler has a heating output of 30kW and an improved flow rate of 16.4 litres per minute at a 35 degree temperature rise.

https://www.directheatingsupplies.co.uk/news/worcester-38cdi-combi-boiler-review/

The average comfortable shower temperature is approx 40 degrees c. In the summer, you'll get a higher hot water temp (the incoming cold mains will be at a higher temp) and this will combine with your cold to give more flow to your shower. This is assuming your incoming cold mains can provide the higher flow rate - has this been measured?

Even in winter, you should be getting a decent flow rate of around 15 l/min. Rain showers are obviously subjective so it depends on how large the head is. You could try fitting one of those air showers (eg. Raindance) which give the feeling of more flow than is actually available. Or fit a smaller head.

The other thing to consider is the pipework leading to the shower. Ideally, this should have been run entirely in 22mm from the boiler.