F & E tank for Elson Diamond

[StewA]

I have had severe problems with sludge in my CH system. The sludge has now been cleaned out and to try and prevent this happening again I gave the system a dose of inhibitor. This was fine for a few days but then I started getting a strong smell from the hot water.

The water tank is an Elson Diamond and apparently because it is a primatic tank you cannot use inhibitor with it.
My plan is to blank off the built in F & E tank and fit an external tank on top of the Elson.

At present the feed comes out of the tank and is Tee'd into the primary return just after it leaves the tank.
The vent pipe runs down to the airing cupboard and is Tee'd into the low pressure side of the pump.

The tank I am thinking of using is a "Polytank 18l Expansion Tank" from B&Q.

I believe the vent pipe would be ok as it is, but would the feed be ok going to the primary return where it is now? I am concerned about heat travelling up to the F & E tank as it is plastic.

Is this plan feasible or is there a better way to allow me to use inhibitor?
Thanks Stew

 

[Dotty]

OP. You have come on here looking for confirmation that your very bad idea will work.

You've been told no, and why not several times over. You are now arguing with professionals in the field with many years of experience between them because you have not had the answer you think you want.

Do what ever you like. You're getting no more answers from this forum on this particular matter.