Hot water flow much higher than cold

[Teessider66]

I have a 21 year old Heatrae Sadia Megaflow system which suffered for a long time with low-pressure. I would get an initial pulse of high pressure,rapidly falling off. The kitchen tap got about 3 litres a minutes.

There is a stop cock before the cold water combination valve. If I close then open the valve the pressure improves for a few minutes, then tails off.

Yesterday I changed the stop cock and it has made a huge difference. The kitchen tap now gets 8 litres a minute hot, and 4 litres a minute cold.

But why is the hot so much faster? Do I need to change combination valve as well?

 

[martygturner]

Some muck in the combination valve filter ?

 

[Johntheo5]

You may not be using the balanced cold water connection off the HW cylinder PRV (pressure reducing vave, normally set to 3bar) but may have a separate PRV on the cold water supply to your kitchen tap and the other cold water users.

 

[muggles]

Worth noting that you need to be G3 Registered to work on these

 

[Teessider66]

I haven't touched the combi valve, only replaced the stop cock, but thanks for the advicein the valves.

 

[Johntheo5]

Don't think requirement for a G3 if cleaning/adjusting the PRV IF installed separately on the cold feed.

 

[ianmcd]

Yesterday I changed the stop cock and it has made a huge difference.

Do you mean that white plastic valve at the bottom of your pic? if so replace it with a full bore lever valve, those cheap plastic ones are nothing but trouble

 

[jjimjam]

I have a megaflo. When I get increased initial hot water pressure, I recharge the airgap.

There are instructions in the manual and several on youtube.