Hot water pressure drop

[Steve Nunn]

i have a client who has an old (15 yrs +) valient combi. the hot water pressure isn't brilliant, but goes worse if another hot water tap is turned on.
i realise it's a bit vague, but i havent been yet, but any info on what to look for would be most helpful.

 

[oldplumber]

its a combi, an old combi , so only one tap can work at a time as it will only have a limited flow rate. Also the inlet filter on the cold feed is probably full of muck..

 

[villa_tom]

I'd go with the inlet filter too. Had this happen on an old vaillant also. Spoke to their tech support and he talked me through it. Took the filter out and ran it under a tap to clean in then put everything back together and it was ten times better.

 

[Steve Nunn]

Thanks for the quick reponse Oldplumber and Villa_Tom
been to look at it today and it's not a combi boiler setup, it's a system boiler with a HW cyl.
there was a 22mm iso valve on the HW outlet just before the tee for the vent, which as far as i can see in my water regs is illegal.
i replaced the valve with a straight piece of 22mm, but no improvement on the water pressure.
then went into loft to see the pipework, and just wanted to switch light off and run away( i think this system was installed pre water regs days).
there are 3 bathrooms in total, one adjacent to the one with poor pressure has excellent pressure.
the 3rd at the far end of the bungalow has a shower pump fitted to the shower, but the way the pipes are configured, the hot water tap in the bath and basin activate the pump, and have good pressure as a result. is this acceptable practice.
if so the client wants to fit a 2nd shower pump to the 1st bathroom (hope your keeping up) so that the HWwater to the basin can be boosted.
there is more but i will leave it at that for the moment.

 

[gasmarc]

there is no problem pumping water coming off a normal cylinder, I would have checked the taps first myself for a blockage or twisted flexis or isolation valve part closed perhaps ,good luck

 

[Steve Nunn]

thanks for the reply Gasmarc
there are no iso valves on the 1st bathroom basin. however they are pushfit, so a bit of a drain down and temp bypass the HW tap to check the flow (and fit iso's at the same time). the difference between batroom 1 (poor flow) and bathroom 2 (good flow) is bathroom 2 has standard taps with a 15mm feed, whereas bathroom 1 has a mono mixer with 15-12mm tails.
i think i will be a long time on this job.

 

[gasmarc]

I have had an issue before where i had fitted taps that will only work off a combi, ouch that was an expensive mistake