Brown hot water

[Leeky]

I replaced my hot water tank about a year ago. The original one had been installed when the house was built in 1957 and had started to leak. It is an all in one indirect unit that supplies hot water to the radiators and the hot running water. It has one cold water feed unlike a true indirect system that uses two cold water feeds. I am no expert but i believe the tap water and radiator water is separated by some sort of air lock.
The problem arises when the hot water and heating are on together. The hot water is very rusty coloured and you have to run off a whole tank full of hot water before the next tank is clear. This happens everytime. If only the hot water is on without the heating everything is fine. I wouldn't of thought the hot water tank is corroded just after a year.
Please help with any advise.

[sonray ltd]

i take it its a primatic or single feed cylinder.
sounds like you have lost the airlock.
if so the cylinder will need draining to replace the airlock.

[Leeky]

Thanks for reminding me its called a primatic. I had forgotten.
I will drain the tank when i get chance in the next day or so.
Thanks for the information. I will let you know if it works.

[sonray ltd]

the art to getting the airlock back is fill the primatic slow.

[Leeky]

I drained my system and refilled really slow as suggested. The hot water is still really brown when the central heating is on.
Any more ideas please.

[sonray ltd]

it sounds like the whole system could do with a flush out.

[Leeky]

I'm going to replace all my radiators soon as they are quite old.
I know i can't use any chemicals on a primatic system due to cross contamination.
With the radiators removed can i flush the system?

[sonray ltd]

you can use chemicals if you bypassed the cylinder.
but then thats alot of mucking around.

but you can flush the whole system with a hose.
have you tried it with the pump speed lower ?

[Leeky]

I will have a look at my pump tomorrow when i get home.

Thanks for all the advice sonray ltd

[justlead1]

Hi. Just a thought re:- primatic cylinders were in general fitted to back boiler gravity type installations to protect the boilers from corrosion, being a cheap alternative to an indirect system. However they do not cope well with pumped systems. It could be the reason the air lock has been effected? Good Luck