Upgrading a primatic tank

[Graham33]

Firstly have to say thanks for a great site, have learned a lot by reading through many of the central heating problem threads here.

I have an old single pipe central heating system with a primatic tank, running from a 10 year old Baxi Solo 60 boiler. There's no room thermostat control so hot water and central heating are both controlled from a single dial on the boiler.

Over the last year or two the radiators have been increasingly getting colder at the bottom and middle but still very hot at the top. Having read similar threads here it seemed likely that sludge in the system was the problem so I've removed some of the radiators and flushed them through with a hose (thick black water like oil came out) and have also replaced some of the downstairs radiators which were originally single panel with new double panel ones.

The system now runs much better and although the radiators still aren't nearly as hot at the bottom as at the top, I think it's probably as good as it will get without running a new 2 pipe system.

Anyway, I'd like to add inhibitor to the system to prevent the corrosion/sludge problem happening again, but it seems you can't do that with a primatic tank... so I'm wondering how big a job it would be to change to a separate tank for the central heating system?

Would it be as simple as fitting an extra tank in the loft to feed the central heating and leaving the primatic tank in place to handle the hot water as it does now? Or would it need 2 new tanks and another pump or anything else?

Thanks.

 

[waterworks]

Hi you will need to change your primatic cylinder and fit a indirect cylinder, also you will need to install a feed and expansion tank to feed the heating.
As your existing hot water must be gravity you would need to change this to pumped which would require control valves and thermostats etc, so quite a big job.

 

[andytheplumber]

I think your better off running a complete new system .

 

[Graham33]

Thanks for your comments guys, I think I'll just leave it as is for now and see how long before sludge build up starts to cause a problem again.

 

[JPC]

how about aluminium rads ?

 

[Graham33]

Think aluminium rads would cost as much as a complete new system so not really worth it on the current 1 pipe system really.

Would it be worth doing a complete drain down and refill every year or two, to combat sludge build up?

Seems 2 or 3 of the original lockshield valves are leaking slightly now (after replacing the rads) and 1 TRV is stuck almost completely closed, so it'll need another drain down and refill anyway.