Best Way to Boost Flow Rate at Bathroom Hot Tap

[_Sid]

There's clearly quite a lot to it. I miss my combi

 

[Madrab]

I thought of that, but didn't think it very likely. Worth checking anyway. I believe it's not allowed for a shower, as mains failure could result in scalding.

With a manual gravity fed shower then yes, that's how it should be. Do installers all follow that, certainly not, do a search on shower with poor HW, tends to be unbalanced supplies that are the cause where many bathrooms are on cold mains and gravity hot.

Thermostatic showers are a bit different and most would normally fail to safe and shut the flow down if the cold drops out or the temp exceeds the set temp by a certain margin. Most are either Anti scald or TMV2/3.