Water pressure in bathroom shower - help with your experience please!

[YireosDodeAver]

Just had a new bathroom fitted and I want to know whether this problem is (as my bathroom fitter claims) "normal" or whether he's trying to pull the wool over my eyes.

We have a mixer valve setup which can divert the water flow to either the shower head or the bath filler tap.

In the handwash basin, the hot water flows at a good rate - you can fill up a pint glass with boiler-hot water in less than 3 seconds.

Just next to that, the bath filler tap flows at less than a third of that rate - it takes just over 9 seconds to fill a pint glass.

The fitter says it's normal to have a lower flow rate through a valve because of the filtering and I can accept that there might be a reduction but a cut of flow-rate to a third of what it could be seems ridiculous to me. I think there must be a fault in the installation but I need data.

Could you do me a favour if you have a mixer/diverter valve like this and fill up a glass from your bathroom sink and from your valve setup and tell me roughly what the difference in flow rate is for you?

Depends on the internal bore of the fitments.

I think my shower (thermostatic mixer is a good pressure).
I got an add-on to have an overhead and a hand-held attachment (as I'm having a bathroom fit and considering this and wanted to see if I like the overhead bit).
The flow through the add-on (same thermostatic mixer) was a lot less than without it, as the selection valve had a much smaller bore.

My parents just had a new bath and shower fitted in their second bathroom and the shower is very strong.

It's no weaker than the handbasin

With a mixer valve set up going on

It also depends if your water supply to shower is from a water tank in the loft or direct mains supply. Some showers are only efficient from mains supply.

I presume it's a thermostatic mixer valve? Have you googled to see if anyone else has this problem?

What do the specs say for it?

Thanks for thoughts.

Well after spending a morning prodding it he reckons the valve may have a faulty cartridge and is going to see if we get an improvement if he replaces that bit.

We will see whether that works.

I would still appreciate actual numerical data from anyone with an equivalent setup, for how much less the flow is through the valve compared with through a nearby tap.

It's a thermostatic diverter valve fed directly from the mains for the cold supply and from a combi-boiler (also fed directly from the mains) for the hot supply.

Just checked both mine and they are the same pressure for the tap and shower. I would have been suprised if they were different. They are reasonably high end ones.

Funnily enough my son recently had one installed and had the opposite problem with the shower having too low pressure and the bath tap being ok. Other people online had the same issue. My son emailed the company and they replaced the divertor valve and the shower now works ok. He was lucky as the divertor valve was not an integral part of the unit so it was easy to switch over.