Hot water flow rate through thermostatic mixing valve

[mpd5]

Hi, I have a 22mm thermostatic mixing valve (in a rest home). it is sited about 5 metres from the bath. Recently the hot (mixed) flow has diminished significantly. I have cleaned the mesh filters and the check valves on the inlets. The hot water feed seems ok at the kitchen tap on the same floor which is not controlled by a valve.

having reassembled the valve the hot flow in the bath now seems to pulse every 10 secs or so as if the hot water is struggling to get through the valve.

Do you think the valve needs replacing (its been working for about 8 years). Also could I put a pump before the valve on the hot feed to boost hot water pressure or is this a no no.

the hot water tanks are on the ground floor as is this bathroom and valve and they are fed by cold water tanks on the fourth floor so there should be plenty of head, however the pipe from the hot tank does run up then along the ground floor ceiling then back down to the valve cupboard.
Hope this makes sense. Thanks in advance for any advice.

 

[buck51]

Hi, Does the temperature alter with the pulseing flow rate,
Try adjusting the temperature from one extreem to the other
Is there a good flow in cold and hot possitions,if yes then try resetting to normal temp
if not it may be starved of hot or cold supply

 

[mpd5]

Thanks for the fast reply buck51, the cold and hot supplies seem ok though not measured apart from flow rates at the kitchen sink. Temp does not fluctuate when pulsing.

I am going to replace the valve tomorrow so I will let you know how I get on.

Any thoughts on the pump fitting? (I fancy this idea because I think that the thermostatic mixer valves do restrict flow quite a bit?).

I may be wrong about that though...!

Cheers.

 

[mpd5]

hi buck51,

Yesterday I replaced the mixer valve with an Intamix adjustable valve. The flow rate has quadrupled and has solved all my problems. I took the old valve apart but could find no debris or anything. I can only surmise that he springs have weakened over the years.

The new valve was £39 plus vat, but it was well worth it to have the issue resolved. Thanks again your your comments.

MPD5