calama

Ok thanks, yes I think that will have to be the plan. The system does have a mag filter on it and I flushed out the manifold separately...there was quite a bit just sitting in the bottom on the manifold so likely there is something in valve too.

Yes it it clearly marked hot and cold on the valve. The installation is around 15yrs old now and used to work ok, but last few years has struggled.

Hi I am wondering if the mixer valve would normally affect the flow rate? If I set the temperature to anything above 45deg then the flow meters barely register. But if I set it to minimum then I get 2lt/min at the flow meters. I can't get the correct temperature at the right flow rate to get a large room heated up. I would expect the mixer would just mix the hot input and cold return without affecting the flow...am I wrong or is it defective? Thanks for any advice.