Replacing honeywell 3 way diverter valve without draining

[Farooko]

Hi there

I have an open vented CH system with the two water tanks in the loft (one big and one small F&E). Can I replace the diverter valve by putting the bungs to the two pipes (one inside the small tank and one pointing towards the tank)?
I just dont want to drain the whole system down as Ive heard that its a bit%$ to remove air lock in some cases.

Thank you

 

[kidgreen61]

Yes you can, you need a good seal on both, and you will have some water come out when you undo any union.
If there's an auto air vent on the system, close it.

 

[ianmcd]

Post a pic of the valve that you have , there is a good chance that you can just change the actuator without draining anything