To flush or not to flush (CH)

[AnthonyL]

I'm coming to the end of the first year in this house and seeing as winter is nearly here thought I should get the boiler checked which is booked for Monday.

However I now wonder whether I should get the 11 radiator system flushed and I'll discuss that when the service man arrives but I want to be prepared. Over the phone he's said around ?340 - cleaning out, running on low with chemicals for a couple of weeks, power flush (I think that was the sequence).

The boiler is a Baxi 105HE and the vendor says it was put in around

2007/2008 though there is no paperwork. I got him to get it serviced last year and that required a new gasket and flue which seems a lot for a not very old boiler. I also know he was financially stretched and would have done everything at a minimal cost.

A couple of photos at:

Am I right in seeing that there is a drain point at the bottom right (there is a square screw in the end) and that the system is rigged for easy flushing (the flexible pipe). I don't know what the top-up arrangement is - any idea how to find out?

I can hear light "tinkling" in the radiators (yes the heating is still on), and a couple of radiators "sing" but that might be the TRV valves as giving them a bit of a turn fixes that for a while anyway.

Is it easy to see whether the fluid is in a bad state? The water around here isn't very nice, seems to leave a brown/black residue on my toothbrush.

?340 is quite a lot of money - don't know if I'm confident enough to try it myself and need to ask the right questions on Monday. I've read the Wiki but any further advice welcomed. Thanks.

(PS If anyone is going to rubbish the Baxi please support it with an alternative).

Oh - and is flushing going to save me any energy or is it pure maintenance and radiator longevity?

[NY]

I was expecting from the title that this would need an answer such as:

If it's yellow Let it mellow

If it's brown Flush it down

:-)

[Martin Barclay]

Umm...that sounds more like something in a toilet pan!

[John Rumm]

With HE boilers its important that the system be flushed and made scrupulously clean prior to installation. So hopefully that was done. (if not, then the damage is probably done by now).

As long as its been properly treated with inhibitor since, there is unlikely to be a need to do it again.

Do you have a filter device in the system? If so, drain that and see what the collected "stuff" is like.

Yes, that is *a* drain point. (there may be others in the system depending on the pipe layout)

The flexible pipe *is* the topup arrangement. There should be a pressure dial on the boiler somewhere to indicate the system pressure.

You can also use the filling loop to inject water for flushing. Although its only going to flush in one direction. You also need to take care to

*not* do the initial flush with the boiler actually in circuit (i.e. you don't want to shift all the crud and dump it straight into your HE). So you may be better draining or injecting the flushing water at a radiator position rather than at that drain point depending on which locations let you flush the majority of the system without going through the boiler (you can use its service valves at the base of the boiler to isolate it from the system)

That might be air (or other gas) circulating. Check the inhibitor level, or if in doubt add some more.

Its not difficult to do (mains pressure) flushing yourself, although a bit tedious and time consuming.

Only on a badly sludged up system. (minor sludge may also cause premature failure of the boiler, so that will also cost money but for a different reason!)

[harry]

It's not possible to remove ALL the crud in a system by simple flushing. The best that can be hoped for is to dislodge loose crud that might move an d settle in the boiler. The only way to remove it all is to remove each radiator and flush out with a hose. There's probably not a lot of benefit in this and the possibility of starting a leak. A good thing to fit is one of these magnetic filters that catches most of t he crud which is mostly iron (oxides) which you don't want in your (probabl y aluminium) new boiler. You can open it from time to time and see if the inhibitor is doing it's jo b. There may be a little crud initially but later none.

There are different inhibitors depending on the metals in your system.

[AnthonyL]

I'll see if I can find out from the vendor but with the lack of paperwork and knowing other things that have been bodged in the house it is a worry.

I don't know - where would it be?

Yes there's a pressure dial. It's reading 1 bar at the moment (recommendate range 1 - 2.5 bar). I presume this is incoming mains pressure? So the radiator system is all at mains pressure? If so what happens if there is a leak when on holiday?

This sounds the most practical path plus a double check that there are no cold spots on the tops of the radiators.

I'm not sure that I'm fully up to not messing it all up.

Thank you

[Andy Burns]

The filling loop isn't intended to be left permanently connected, (though I gather most are) meant to fill to pressurise it, perhaps relieve pressure if it's above the max, then disconnect.

If the valves at the end(s) of the filling loop are left turned on, it'll be a very big leak!

[Brian Gaff]

I was wondering where this person was to be thinking of Winter. Brian

[Brian Gaff]

Exactly. go to the top of the class. Actually I do not have any central heating which requires plumbing. I wonder if somebody could make a system using microwaves running through waveguides to graphite loads where the radiators would be? Brian

[AnthonyL]

Ah - looking more closely at my photo it looks as if the pipe in either feeds to the boiler (default) or turn the tap to feed the radiators.

Ok - so I'll just lose the water in the radiator system as thing stand.

[AnthonyL]

Bloody felt like it this past week or so. Touch of sun so far today.

[NY]

Precisely. I saw "to flush or not to flush" and didn't notice the "(CH)" on the end, and remembered the old Boy Sprout motto for conserving water on Scout Camp holidays :-) I imagine Girl Guides are taught the same thing.

[John Rumm]

No, the mains pressure will be much higher usually. You will the system until it reaches the required "cold" pressure (typically abound 1 bar), and then turn off the taps and ideally disconnect the flexi pipe.

You can't use the filling loop to relieve pressure - there should be a non return valve on the heating side to prevent escape of contaminated water.

Indeed. One of the advantages of a sealed system is that there is only a finite amount of water than can leak.

[Another John]

The _bloody North of England_: incessant rain this week, and 12 deg on Tuesday. Yesterday we had a bit of a respite, and it didn't rain for almost all the day. Last week I was in Montreal: around 30 degrees all the time, and they expect 20-30 the whole summer. (They get proper winters there, like, but at least the city authorities are properly geared up for them.)

J.

[rick]

Recently did my sons system .... drained out all that was in there run on fresh till hot drained again ... then filled and added a cleaner. Left it run for a week (rads were in use) then did drain & flush again ... then refilled adding inhibitor.

Cost was under £20

You can save a lot of money doing it yourself ...

[AnthonyL]

And I guess I could cause a lot of damage :( *

Did you back flush? Where/how do you add the cleaner? How did you avoid sludge being driven into the boiler?

*eg my car MOT and service was due yesterday so I thought I'd just go over things to ensure no avoidable costs. Thought I'd clear the crud out of the cigarette lighter which sits vertically next to the gear stick. Used a screwdriver forgetting that the point was still live when the ignition was off and thinking I was steady enough anyway. Flash - all auxiliary power outlets out of action.

[NY]

Been there. Done that. Quick trip to Halfords needed to buy a 15A fuse. What was frustrating was that I had bought a big box of fuses ages ago so I looked for it in the boot and found that the fuses on this car are a smaller size than on all the previous cars I've owned - I wish they'd use a standard size now and for ever more. I ought to buy a box of these small fuses - much cheaper than buying them one at a time - but knowing my luck my next car will yet another size of fuse :-(