Isolating mid position valve

Plumbers don't fit isolation valves around the mid-position valve as it is not good practice, but if you want to yourself that's your call but the chances of them working when you next want them are very remote.

 

If you want to do something like that then I would use full bore quarter turn valves as they are a lot more reliable.

 

You don't need to drain the system to replace the 3 port all you need to do is bung the system and replace it, no hassle most of the time.

 

Honeywell all the way. In my last house, The valve would have been a pain to change so I bought an identical valve and just changed the motor and circuit board when it failed in the middle of winter.

 

Unless it's a system boiler of course, then could get messy!

 

good point nothing to bung, draining necessary in that case

 

IMHO Any isolating valve on a primary boiler circuit is likely to:
(a) sieze up after a few months
(b) Leak prematurely- especially the ball type (full bore or not).

Reason? Boiler water contains grit, sludge and acidic material. These valves are only suitable for "pure" water (e.g. your kitchen cold mains tap).

diymostthings.

 

Yeah as above I wouldn't put iso valves on it, just drain it down and stick a Honeywell on there. Chances are you will only need to change the head in future anyway

 

In that case use a Drayton they clip off rather than screw off