Magnetic filter

[Machra]

Just moved houses and the central heating (gas, normal (not combi) boiler, microbore pipe work) is making a knocking noise through the radiators. Boiler has been regularly services, paperwork to prove.

I was thinking the cause was maybe sludge and read up that microbore doesn’t like being powerflushed so thought of fitting and using a boilermag filter. Fit filter, dose with flush, etc.

I have three questions if I may.
1. Is the knocking/banging radiator noise likely to be caused by sludge?
2. Will fitting filter and flushing system that way be ok? I was looking at powerflush but there is a lot of info on not doing that with a microbore system.
3. I thought I may as well fit a filter anyway but Boilermag fitting instructions say fit on return after last rad and ‘advise’ against fitting anywhere where it may freeze. My problem is my boiler is in a cold garage which may get down to freezing temperatures. I could fit earlier in the return but that would be before the last rad. Would his be ok or do I fit it just before the boiler and risk it freezing?

 

[Madrab]

No, sludge doesn't usually cause banging, excessive sludge in a radiator would manifest itself by the radiator not heating up properly.

Microbore doesn't lend itself well to powerflushing due to the narrow bore and if it's using reducing manifolds then can actually make things worse if any crud is pushed into them

If the boiler or it's pipework never freezes then neither should the filter, if your worried then it can be insulated, as your pipes should be.

 

[ianmcd]

most likely a TRV causing the banging

 

[Machra]

Thanks to both of you for taking the time to reply. My system uses microbore manifolds and as such I think I will give powerflushing a miss. I have removed most of the rads to clean them when we moved in (house was in a disgusting state when we moved in) and I ran a hose water jet through them then so most should be ok. I did remove the trvs and clean those so I will have a look at them.

I suppose my question re the magnetic filter is whether it will work as well if I fit it in a position (inside the house) that means it is fitted before the last rad in the return feed and not as is instructed in the filter fitting instructions where it says fit AFTER the last radiator in the boiler return feed.

 

[DP]

It goes on the return to intercept water and sediment before entering the boiler
If you are that worried, instal it on the flow
Go for megnaclean, I find it to be the best for catching sediment.

First was a Hive or a Nest every other post, now sludge or low gas pressure