Just found this newsgroup and discovered that there are more than 14,000 headers to download so forgive me if this question has already been asked:)
I have a gas central heating system with 6 heaters. It is at least 10 years old. When I switch the heating off for a long time (over summer) there appears to be a large build up of air in the system which gets stuck in the pump which then needs to be bled. Scottish Gas came to fix and told me that the build up of air was actually gas which was coming from various nasty stuff inside the heaters and provided me with a hefty quote to flush out my heating system. My question is this: can this be done diy (husband is quite good at it) and if so what does he need in the way of equipment and chemicals etc.
You should be running your central heating with a treatment such as Fernox to inhibit corrosion. Scottish Gas are probably correct about the cause, but also probably mercenary about the cure. Depending on your type of system (easiest if you have a system with a header/expansion tank in the loft) you need to add a flushing compound and run it for a few days, empty the system, then refill and add an inhibitor. There are various interesting (and boring) discussions about flushing a little further back in the NG - you can always use Google to search the NG postings if you can't face downloading all the headers. There should be at least one central heating FAQ floating about. Try
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for starters. No doubt the plumbing pros will point you to more resources. HTH Dave R
If Scottish Gas is anything to do with British Gas ( i.e. really Centrica) they are useless & expensive. Flushing was covered very well by Andy Hall in a posting. Search on groups.google.co.uk for Central +heating +flushing +Andy +Hall
Don't forget to put corrosion inhibitor in when the system is refilled.
The build up may well be hydrogen gas, rather than air. Hydrogen is the product of corrosion of metal components in the system. In addition to the pump, you would expect to find it gathering in the tops of radiators. You can easily test whether it is hydrogen by opening a radiator vent and applying a match or other flame. Hydrogen burns with a pale blue flame.
Corrosion happens because of the reaction of the heating water and the metals of the system. It can be almost completely prevented by adding a corrosion inhibitor to the system and topping it up as required - typically every three years, or if the system is drained. At around £20 for the inhibitor (Fernox MB-1 is among the most common), this is rather a cheap insurance policy.
Corrosion is accompanied by the heating water being brown or even black and a build up of sludge in the system. A typical place for sludging is in the bottom of radiators. The tell-tale sign is a triangular shaped cool area in the centre bottom where the sludge is.
If the trapped gas is air rather than hydrogen, then the cause is likely to be different - typically air being sucked into the system through the system vent. This is generally caused by the pipework not being organised correctly or the pump setting being too high. It should also be fixed, because if air is pulled into the system, apart from being annoying, it does promote corrosion.
Well, what a surprise!. I bet the quote was several hundred pounds, right? The typical offering is power flushing which involves circulating a chemical cleaner under pressure around the system. The margin is outrageous as you probably guessed. BG are notorious for this. If you do decide to go for this route, shop around for a fair price.
I had a colleague who was taken for about £800 for this job for about
8 radiators in a flat. The job was bungled and the problem, which turned out to be something totally different, was not fixed. My colleague refused to pay and the contractor threatened legal action in the Small Claims Division of the court. His bluff was called and the case was dropped. The contractor saddled up and rode into the sunset.
There are various things that you can do on a DIY basis.
The first thing is to identify how bad the problem is. The easy way to do that is check for sludging as described and look for evidence of poor heating of radiators.
You can also drain the system and remove a radiator to check. Look for sludge in the radiator. A word of warning. Sludge from corrosion in a CH system, and the water is a superb indellible brown dye. If there is a lot of sludge, then power flushing may well make sense, because there is probably also a lot of build up in the pipes as well. You can hire the equipment and buy the chemical at hire centres. Instructions are supplied, and it is a very easy job to do.
Another approach if there is not too much sludge is to remove each radiator and clean it by flushing outside with a hose or pressure washer. You can flush water through the system at each radiator valve to clear silt from the pipework, again if the build up is not excessive.
If the system is relatively clean, and in any case after the last method, you can flush the system and drain it and then refill with a flushing agent (Fernox and Sentinel among others make these). These are left in the system for a week while it is run hot and then drained and flushed.
My experience was a lot different to this with British Gas. I had them power flush an 8 rad system for £460 and yes, I did have problems (mostly noise) caused by the flush which were all resolved by BG in the original quote e.g.
A new heat exchanger in the boiler. Re-worked pipework in the airing cupboard. A new C/H pump. A second power flush because there was still muck in the system from a dip in a pipe in an inaccessible part of the system.
There were still minor problems 12 months after which were picked up on the annual boiler service and BG returned and fixed these FOC.
Oh! and three months after the original works were completed and the bill paid, BG sent me a cheque for over thirty pounds as a rebate because they over quoted the original job as they had not deducted a discount because of my maintenance contract with them.
As an extra issue to this, under the British Gas warranty of these works, provided I allow them to inspect and replenish the inhibitors (I pay for the inhibitors) every two years, they will re-power flush for free if needed in the future (very likely in my ageing system).
I am pleased that you are happy, but you are paying a lot of money for this.
Do you realise that you can hire a power flushing machine for £36 for half a day or £42 for a full day? You can *buy* the machine for £900.
They would have had to replace the heat exchanger and the pump as part of the maintenance contract anyway. That is costing £140/annum IIRC, and in most years you would be getting a service with a cost value of no more than £50. With this over several years and the margin on the power flush there is plenty in hand to cover these eventualities
If you were taking care of the system yourself, you would typically part drain and add inhibitor every 2-3 years anyway.
To be honest, if the system is clean and maintained in this way, it is very unlikely that it would need power flushing. I used inhibitor in my system from new and maintained it religiously. During a refurbishment a year ago (when the system was 17 years old, there was virtually no build up of sludge (just small amounts in the bottom of a couple of radiators) and flushing produced a little copper swarf that was the original from when the system was installed. Almost all the radiaotors have been retained, with a few being sized upwards to allow lower operating temperature with a condensing boiler.
I'm pleased that your experience has been good in the sense that the system is in good order (now) and you are pleased. However, it is very much akin to domestic appliance insurance. You pay a lot of money for it.
I used to have a BG annual cover policy. However, I had occasion to use it when the thermocouple on my old boiler failed and prevented it from firing (as it should). I called BG early in the morning expecting that they would attend either the same day or at the latest, the following day. I was asked whether I had anybody "at risk", meaning small children or the elderly in the house. I didn't but pointed out that I did have a contract. The earliest that they could manage was five days later.
I cancelled the contract and after a lot of hassle, obtained a full refund. They still appear to be operating with the old monopoly attitude that they are doing one a favour to even show up. If they were operating on a limited public budget then prioritising the vulnerable might be reasonable. When they are operating on a commercial basis and charging an arm and a leg for a contract, it is not.
I replaced the thermocouple for a cost of £3 in parts from the local plumber's merchant.
I have an open case with the ASA about BG's advertising of these contracts, especially the "paramedics" add with the "experienced fitter" and the dopey boy. They are creating the illusion with this that they are providing an emergency service when they are not. It's almost as though Alastair Campbell wrote the copy. The advert is completely dishonest in the impression that it gives the customer.
As I say, if you are happy with what you are getting and paying then that's fine. However, the "peace of mind" may not be what you think and is not coming cheaply. In a year or two you will "need" a new boiler. When you receive BG's quote, make some comparisons with local firms and I think you will be shocked.
Several experts have replied, but I havent seen any of them say that if the system is open vented, you need to check for over- pumping. (see the FAQ). I bet Scot. gas didnt check either.
Andy, After being "in the trade" so to speak since 1965 both as a tradesman and a general foreman I understand the costings very well and whilst not adverse to "having a go" I learnt a very long time ago that perhaps sometimes you pay "for the knowledge" rather than the actual work as this can save a large amount of cash in the long run - look at the number of requests for help in this group as a result of a lack of knowledge.
In this instance Andy no - it was the flushing chemicals that caused the problems with the heat exchanger and the pump was noisy and part of the original contract.
With regards to the maintenance contract - over the years I have use their services on average of perhaps four to five times a year with about half of those times requiring spares - I estimate that I have broken even on the contract subscription and certainly paid less than calling out a private contractor.
Snipped
Andy, after my years as foreman on housing maintenance, which included heating repairs on solid fuel, electric and gas and seeing the results of some of the amateur work (and near fatalities due to carbon monoxide poisoning) I'm afraid that as I do not have the technical qualifications or the detailed knowledge, I prefer in this case to let the professionals do the work. Hence the reason I do not advise in this group on either gas or electrical queries even though I have a general knowledge of both and capable of doing the work.
On domestic appliance insurance I quite agree - it's money for all rope and I refuse to pay for it as most repairs are minor anyway.
I have been asked the same questions and I have had to wait - BUT as I can determine as whether the repair is urgent or not and I have separate forms of heating and hot water it has never been a problem. When I have told them that the works are urgent, described thy symtoms and the asked the telephonist to get an engineer to ring me when THEY have been unsure all my urgent stuff has been done the same day.
I have never had this attitude to be fair.
Again when I have had a "true" emergency they have always responded very quickly to do the emergency repair to make safe etc but I have to wait some lengthy periods for spares for my out of date boiler a few years ago.
Changed my boiler about eight years ago Andy when my old and very outdated Pottertern Neataheat finally broke down and spares were unabtainable (just before Christmas as luck would have it). The cost of supplying and fitting my new boiler £800 and half a day to fit it and because the design of my heating system is rather "cranky" to say the least - (and that is another saga is it was fitted when the house was new and a long time before my occupation) - another half a day to get the water flowing and the electrics working - plus new thermostatic valves supplied and fitted for free in all my bedrooms.
With regards to quotes from other sources, yes I have done that and I also know various qualified, corgi registered plumbers who could "do it on the cheap" but I have found with British Gas in my area of South East Wales, that when I get a quote off them it is never the cheapest but the do the job for that price whatever the complications and the NEVER quibble or argue about their warranty work.
And yes I do bitch about the cost with their reps call and haggle like hell to get the price down or freebies :-)
What kind of system do you have that it needs 4-5 callouts a year?? I would seriously consider a complete replacement. I would not be prepared to live with a CH/HW system that required that much attention.
In our last house, we had conventional gas CH/HW. In all the time we were there, I cleaned out the boiler every couple of years, checked the CO at the same time, and added inhibitor. That was about it. The only things it ever needed was a new thermocouple and a replacement pump.
In our current house I installed our oil system just under 2 years ago, and haven't touched it since.
Didn't that strike you as somewhat incompetent? They should be using the correct materials fo rthe job.
I'm sure you're right regarding costs on this basis, but there is something seriously wrong with a system that breaks down every 3 months. Again, I would be suspicious that BG are not doing a proper job.
That's fine and the main point of DIY is knowing when not to do so.
However, you can shop around for services. I would have thought that your experience would tell you when you have somebody competent and are getting a good deal. Your heating system experience sounds like neither to me.
That is the whole problem with all of this - people accepting poor performance. Their contract should specify a maximum response time and there should be cash compensation for failure to meet that. It is how services should be provided by a professional organisation, which leads me to believe that either BG don't understnad this or that they do and are understaffing in order to make more money. Both are totally unacceptable.
I also have backups for both heating and hot water, but that is not the point. If I pay for a contract that they market as being an emergency service, that is what they should provide, not something based on degree of apparent social need.
"M. Damerell" wrote in news: snipped-for-privacy@sun.rhul.ac.uk:
To quote Andy Hall, yesterday, in this thread
"If the trapped gas is air rather than hydrogen, then the cause is likely to be different - typically air being sucked into the system through the system vent. This is generally caused by the pipework not being organised correctly or the pump setting being too high. It should also be fixed, because if air is pulled into the system, apart from being annoying, it does promote corrosion."
1) Fernox products have been on the market for donkey's years (at least 25) and the results are well known and demonstrated. The Screwfix product may well be the same stuff but is an unknown.
Having used the Fernox stuff for over 25 years I *know* it works.
In the context of a heating system costing typically £5k on a commercial basis, £20 is neither here nor there.
I think it might already be too late - I've got no idea how much inhibitor is in the system, I suspect very little and one rad has already rusted through from the inside.
Pete
(A colleague of mine actually said "LOL" to me once!)
I'd advise caution here too. Heard of a guy who applied match as he opened rad air bleed valve. It was combustible gas and the resultant large flame startled him and caused a large burn mark on his wall.
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