3 way valve problem

[mikej100]

I am about to change the 3 way valve on our system as each time the hot water is heated the rads get hot.
i'm quite sure it has been corroded by hard water and so it's likely that there will be scale in other parts of the system as we don't seem to get much more than a few inches of bath water before it goes cold.
so whilst changing the valve is there anything else i can do at the same time to improve the performance of the system perhaps clean the tank it has an Elson Diamond indirect water tank (antique) or add a limescale remover can anyone recommend a good one.

Thanks
Mike.

 

[seco services]

you can use fernox DS3 in the cylinder.