Temporary leak into tundish when boilers fires up

[Nobblers]

Response from plumber: The expansion vessel can connect to either side I believe as it is past the none return valve but if it is still leaking I think I will tee into the 22mm pipe below the multifunctional valve. If it still happens after that it would have to be a faulty expansion tank.

 

[Nobblers]

Yeah as @scott_d says expansion vessel is connected in the wrong place. Should be tee'd off the cold feed to cylinder, it's currently in the balanced cold connection of the combination valve.

Nice one

 

[EvilDrPorkChop]

Response from plumber: The expansion vessel can connect to either side I believe as it is past the none return valve but if it is still leaking I think I will tee into the 22mm pipe below the multifunctional valve. If it still happens after that it would have to be a faulty expansion tank.

He's wrong, as if that was the case you'd get back feeding from the hot (Cold feed to cylinder) down the balanced cold.

 

[Ricky]

He's wrong, as if that was the case you'd get back feeding from the hot (Cold feed to cylinder) down the balanced cold.

I agree with the above, if you are going to connect into the multi block it has to go into the connection on left hand side (photograph) not the top right, as said previously that is for the balanced cold water, it is before check valve, partially blame manafactures as their installation instructions are not clear on how to connect to the multi block,