I've bought a new boiler

[Phil L]

And would like some information WRT fitting it. (please no lectures about Corgi registration claptrap)

The old boiler is still working, but not efficiently, and I have to do jobs on it daily to get it to do it's thing, bits of elastoplast here and there, string, elastic bands etc and not least, top it up every 6 hours due to an expansion vessel problem - anyhoo, within days it's going in the skip, so hurrah! etc.

My main question is about the radiators - they're quite old, at least 15 years, but the plumbing to them and to the existing boiler is only about 8, my idea is to leave everything in place and just swap the boiler, brilliant! - except....over the past few years, what with all the topping up etc, there has been no inhibitor in the system and the water now is akin to crude oil. I took off all the downstairs rads last year and took them into the back garden for a spot of hosepipe therapy, and the patio is still stained black, so my question is this; should I take off all the rads and flush them out manually (this is not a problem, even with the upstairs ones), or should I use some other method of flushing out the system, which will also clean out the pipework inbetween the rads, if so which / what, and how much? - bearing in mind that I have just forked out my last £240 on a new boiler.

TIA

[Toby]

You don't say if you also have a hot water cylinder, heated from the boiler... If you do, you need to treat this as another radiator when flushing out (but you don't need to disconnect it and take it outside unless you really want to!

I would suggest doing the following...

Drain system completely (So release as much water as will come out, then undo all the bleed screws, starting with the highest ones)

Turn off all rads, both lockshield and TRV/normal valve (Making a note of the number of turns on all the lockshield!)

Remove and hose all rads one at a time, and then replace on wall, but leave switched off.

Remove old boiler (that's the thing that heats the water, not SWMBO! (removing SWMBO during the work might be wise though!)

Connect a hose to the pipe that was connected to the boiler CH return (so water was flowing out of this pipe into the boiler), and direct the other end to the drain (not the patio!)

Connect another length of hose from the tap to the CH pipe that had the CH water flowing out of the boiler

Fully turn on the last rad in each branch of the system (In mine, the boiler is in the middle, so upstairs and downstairs are effectively two separate branches off the boiler, if you get me) both the lockshield and the TRV (AND CLOSE THE BLEED SCREW on all the rads!)

Make sure all the rads are off, except the last ones on each branch (It is actually better to do one branch at a time.

Turn on the water and flush the pipe work (as the bleed screw is not open, the radiator will not fill up, water should just flow along the bottom)

Run the water until it's clear on this branch

Now, open the next radiator along this branch (REMEMBER THE BLEED SCREW!) and then (and only then!) turn off the previous radiator.

Go round all the radiators like this, and this should flush all the crap out.

If you don't have TRV's fitted, do this now, while the system is drained!

Refill and bang in some inhibitor

IANAP (I am not a plumber!), this is just how I would personally approach it!

Toby...

[Toby]

Just to add to this, I would also refill, drain and refill again.

Check for leaks, then when you are 100% sure all is OK, add the inhibitor.

If you have any motorised valves, then say so before starting!

Toby...

[Heliotrope Smith]

You flushed all individual radiators only 1 year ago so no problem.

Put in a system cleaner BEFORE fitting a new boiler and run it for a couple of days minimum.

Drain, refill and run a couple of hours. Drain, refill, run and drain. If now the water comes out clear then fit new boiler. Another fill and flush is recommended after the new boiler is fitted.

Cost is just the price of the system cleaner plus the inhibiter when all up and running.

[Phil L]

Thanks for replies up to now - I'll check back tomorrow and in the meantime, I'll have a think about what's been said up to now.

[geoff]

In message , Phil L writes

Yeah, you can stick some power flush in there , leave it in for a couple of weeks , it should get rid of most of the crap

[John Rumm]

I would start by adding a chemical cleaner now and leaving it running with the old boiler for at least a couple of days - preferably a week or more.

I assume you are going for a sealed system rather than vented?

If so, then since you have flushed the rads not that long ago, you can probably get away with doing them in situ this time. If you have not got a decent drain point you need to add one (a hard piped one that has a service valve on the inside, and a pipe that goes through a wall to a gully outside is the easiest to use). To flush, turn off all rads but one. Open the drain valve, and open the filling loop so you are directing the full mains flow through the pipes and that one rad. Let it flow until it is running clear. Once that one is, open the valves on the next rad, and then go back and close them on the first (by doing it in this way you can just leave the filling loop tap open). Rinse and repeat until you have run out of rads.

[Doctor Drivel]

Put in X-800 and follow the instructions to the letter. Flush, remove old boiler, fit new boiler, fit a magnaclean filter on the CH return pipe. Fill, flush, insert X-100, monitor filter for 1/2 day after running system, clean filter,. monitor filter every week and clean until no more debris collected. Clean filter every year. Insert X-100 every 4 years, no need to flush.

[The Medway Handyman]

Exactly what I did to our 25 + year old system, no problemo.

[Edward W. Thompson]

To flush the system of magnetite in the water you need sufficient water velocity through the system to entrain the 'sludge'. You won't get this by draining down from the header tank.

Your 'best' approach is to put some of the proprietary cleaning products into the system and leave for a couple of weeks, that should loosen 'stuff' not already entrained, then removed all raiators and flush them through using a garden hose.

As your system seems severely contaminated, before replacing the radiators, I would bridge each radiator 'space' in turn with a 'temporary hose, break the system at its lowest point, shut off each radiator valve except one with the bridge and starting at the top radiator and flush each 'leg' using the header tank as source.

[tony sayer]

You wouldn't want to be doing that this weekend, it seems its going to be nuts of the brass monkey weather;!...

[DavidM]

Check the guarantee for your new boiler. Some manufacturers say the guarantee will be invalidated if the whole system is not power flushed after installation of the new boiler.

[Doctor Drivel]

I would like them see that stick in court. What they want is a clean system. Put on a Magnaclean and have X-100 inside and they can gripe. No crap then gets into the boiler.

[Phil L]

Thanks for all replies, and this is my plan of attack, prior to hanging new boiler:

1) take off all rads and blast them through with hosepipe, this will take a few hours but I'd rather know for certiain that they aren't full of 'treacle', like they were last time.

2) hang all rads and refil the system adding a flushing additive, run through on a low heat for 30 minutes, or according to manufactuers instructions.

3) Drain system via bleed valve near front door, and rinse thoroughly.

4) Refil system, with added 'fernox' or similar inhibitor.

5) Hang new boiler.

I do realise that plumbers now offer a powerflush, but last time I looked it was £200, and even then it was only as part of a major service or fitting of a new boiler.....I reckon the flushing crap will set me back about £20 and the same again for the inhibitor, so I'll save at least £150, and as an added bonus, I get to play in dirty water for a day.

[Rod]

I think half an hour is a bit optimistic! Can you arrange a few days between adding and flushing?

"Add Fernox Superconcentrate Cleaner F3 via the radiator air-vent. When pre-commission cleansing new systems Fernox Cleaner F3 should be circulated for a minimum of 1 hour at normal operating temperature. For cleansing existing systems, sludge and debris should be dispersed also within 1 hour at normal operating temperatures. However, to remove hardened iron oxides and limescale, the cleaning time can be extended to up to 1 week under the normal heating cycle. If, a radiator still has a cold spot after 1 hour, increase the flow through the radiator by closing the valves on the other radiators. An additional or repeat dose of Cleaner F3 may be necessary in some cases."

[Phil L]

not really as I'm working tomorrow and it's being fitted either on Saturday or Sunday.....I suppose I could get it tomorrow and leave it in for 24 hours.

Ah, but, the rads are being manually cleaned in the back yard - I'll be able to see inside them and there won't be any cold spots.

Thanks for the info.

[Heliotrope Smith]

Sounds good. Go for it. The good thing when you DIY is that you have plenty of time to flush inividual rads

Power flush won't be necessary doing it your way.

Make sure you wear your wellies.

[Heliotrope Smith]

PS. keep sheep out of the garden!