best method for flushing clean ancient cast iron rads

[long-pass]

Hi everyone.
A customer has got all excited and bought 4 old and very heavy cast iron "hospital" rads. they will surely be filled with debris and gunk and as i have installed new pipework and a new boiler they have to be thouroughly cleaned. is powerflushing them the best or is there a chemical i can use? also they have to have the old bushes removed and replaced then pressure tested but thats for another post.
Cheers

 

[diamondgas]

Personally I'd take them outside and set the hose on them, if you can? Give them a good swill about a couple of times and you're sorted

 

[long-pass]

Cheers diamondgas. my back just twinged with the words take them outside. i will give 1 of them a go with the hose and see what comes out.

 

[mountainman]

Depends how clean inside you need them.
You could chemically flush them but for general use Diamond is correct.

 

[jase158]

you can use any chemicals on it, only things you need to be careful of is the towel rads and aluminium heat exchange's.

 

[diamondgas]

Cheers diamondgas. my back just twinged with the words take them outside. i will give 1 of them a go with the hose and see what comes out.

If they're empty most of the debris will be at the bottom. leave the bleed valve closed and swill that should get rid of most of the crud ....... IMHO .. block off the outlet and let the rad fill and drain a few times? You'll never clean it thoroughly even with a machine, they're pathways are too big IMO

 

[jase158]

also testing should be fine too. we did an old house put the same rads back in after they were sandblasted and repainted and it was all tested.

 

[chris watkins]

Take care long-pass, if they are going into a sealed system make sure you put in a disclaimer as they were never designed to have any more than a few Metres head pressure on them. Keep the cold fill pressure as low as you can 1 bar (10M) max if it is a normal 2 story house. Also check / adjust the vessel pressure often pre-charged to 1.5 bar so drop it down to cold fill. While on expansion vessels don't forget these will contain a lot !!! more water than the normal steel jobies so depending on there size the system size & where you are using a built-in vessel in a system or combi boiler it is worth checking that it will be big enough.

 

[diamondgas]

You've got to check to 3 bar at least! had an old wendsbury manifold blow on me this week! Grrrrrrrr

 

[long-pass]

Cheers guys, i just want to get the worst of the crud out so will give them a hosing and a few fill ups and drain outs. the system has a magnaclean on it so i am hoping this will also catch some of the muck. i know most rads are tested to 10bar but that seems a bit excessive do you think testing to 5 bar is too little?

 

[chris watkins]

Even brand new CI MHS ones which have washers between each flange are only rated at a max of 6 Bar, If you / client wants them tested then max 3 bar (safety valve setting 3 bar) but as I say I would keep as low as poss.

 

[long-pass]

Cheers Chris, i did not even think about any of what you said so thanks a lot for your advice, it will hopefully save me a lot of trouble. they are going onto a sealed system running on a combi (WB cdi 27kw) on the ground floor. 7 rads, 4 being the iron rads and 3 of them being large.

 

[chris watkins]

Check M.I's for vessel size & what it can do. I thing its around a max of 8 - 10 smallish rads so I would guess that you will need an additional vessel you can just add a small vessel tee'd into the return.