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juvenal

Combi Boilers And Limescale

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Just seven months after installing a new i-mini combi boiler (£2800 job), I'm having it dismantled to fit a new heat exchanger.

Reason?. Current exchanger already clogged right up with limescale, restricting hot water flow by 90%.

Permanent remedy? An additional and expensive installation to destroy that lime content in the first place.

If you're living in a 'hard water' area (I'm on Dorset coast) and about to install a combi, budget the thick end of another grand to install a proper water softener unit, 'cleaning' all the mains cold water coming into your house/flat.

Older boilers, apparently, don't suffer from scaled up exchangers.

If this problem is currently affecting one of your BTL's - tough luck...

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Just seven months after installing a new i-mini combi boiler (£2800 job), I'm having it dismantled to fit a new heat exchanger.

Reason?. Current exchanger already clogged right up with limescale, restricting hot water flow by 90%.

Permanent remedy? An additional and expensive installation to destroy that lime content in the first place.

If you're living in a 'hard water' area (I'm on Dorset coast) and about to install a combi, budget the thick end of another grand to install a proper water softener unit, 'cleaning' all the mains cold water coming into your house/flat.

Older boilers, apparently, don't suffer from scaled up exchangers.

If this problem is currently affecting one of your BTL's - tough luck...

I was always very sceptical about water softeners, biut a softener solved exactly that problem that I my landlord had.

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Have you got a magnetite filter on the central heating circuit as well? Only costs a hundred quid or so.

Yes. Got one fitted but doesn't solve problem. Thanks for suggestion though.

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Older boilers do get affected by limescale - not as much, because it is the water tank that fills up with limescale.

However, when I was a student, I remember the hot water packing in, in the house I lived in. The university's plumbers were brought in, and diagnosed a problem with the hot water tank. It took 3 men to drag it out. Realising it was probably filled with lime scale, they cut it open. "Filled" was the right word - the entire bottom half the tank was almost a solid chunk of limescale.

That said, building regulations do mandate the installation of a chemical exchange water softener for any form of "water heating" device in hard water areas. Provided that you keep it maintained with salt, they do solve the problem of limescale completely.

A magnetite filter is a good idea on the heating circuit, especially for a modern condensing boiler, where the thin heat exchanger tubes are liable to clogging with corrosion products. Definitely cheaper to buy a filter than get the system power flushed.

Don't confuse a magnetite filter with a magnetic water softener (which are of doubtful value).

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surely water only drops limescale once in the heating system unless you have a leak.

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Was doing some boiler research a few years ago, when boiler belonging to a relative was having problems.

There were loads of interesting posts, on many different forums, I pasted into a Word document. This was one of them. Keep in mind I would not open any boiler myself, would not advise anyone but qualified engineer to do so.

quote: What type do you buy? I always use and specify Gloworms. Their condensing boilers are good value and super reliable in my experience. The first one I put in in 1996 is still going strong.

Also I believe running them at lower temperature extends the life. I always aim to run my systems at 65 or less. Also very efficient.

I installed a brand new Gloworm in my last house. The heat exchanger kept clogging up. The first time I called Gloworm to get a new one they told me it was going to cost me £250!

So, being the stingy bugger I am, I took it out and placed it in a bucket of concentrated caustic soda solution for a day. Clean as a whistle when I put it back. Did this on another two occasions since then.....

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Here's another useful one to keep in mind, although I am not convinced about expensive power flushes - when I buy a house and am in such a position, I think I will run a cheaper alternative idea past my boiler-engineer pal.

When you do get the boiler changed, make sure the operative power flushes your existing system to remove and dirt & sludge, then refills with a good quality corrosion inhibitor (Fernox or Sentinel). It's also worth considering a scale reducer on the inlet pipe to reduce scale in the Heat Excanger and to extend the boiler life. Keep an eye on the operative when the system flush is done, as, from my experience of dozens of replacements, many operatives are lazy and will avoid doing this unless you watch them like a hawk!

You should be left a new CP12 safety certificate, warranty card & instructions for use by the operative before he leaves. You should expect to receive a blue Building Regs compliance card through the post in 28 days after the installation - you will need this in future for the HIPS pack when selling your home, so if you don't receive it - breath fire at the installer until they send off for it.

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Humans have such short memories. Combis were designed during a run of very temperate winters over 15 years or so. New technology is too many times designed for perfect environments..

.

.

Nothing to do with lime scale but reminds me of this in the past..

https://www.avforums.com/threads/frozen-combi-boiler-condensate-pipe-anyone-else.1168662/

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...A magnetite filter is a good idea on the heating circuit, especially for a modern condensing boiler, where the thin heat exchanger tubes are liable to clogging with corrosion products. Definitely cheaper to buy a filter than get the system power flushed.

Don't confuse a magnetite filter with a magnetic water softener (which are of doubtful value).

I know nothing about this stuff, but is a magnetite filter likely the best (value for money) first thing to try with clogging problems? Neighbours replaced their entire warm air heating system and water heater a few years ago to a wet system and boiler - not sure what type - on recommendation from a gas engineer. Don't know whether it's a corrosion or limescale issue but they now have an annual cost of £100+ to unclog the system/boiler and wish they'd never changed it. They didn't say anything about a filter or other recommendation so I might mention it to them; an older couple and could do without the hassle. Also a very hard water area so could be about that.

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Was just following up a private theory; if the boiler is a closed system, can't you just add softened water at the outset to a new boiler?

Can I put softened water in my central heating system?

Yes! British Standard BS 7593:2006 Code of practice for treatment of water in domestic hot water central heating systems has recently been updated and now allows systems, including those with boilers with aluminium heat-exchangers, to be filled with softened water provided that a corrosion inhibitor specifically formulated for the purpose is added and properly maintained.

Although reading to the next part.

Why is my boiler manufacturer claiming that because I have a softener fitted my boiler warranty is invalidated?

Very few boiler manufacturers have carried out testing to access performance of their products with softened water. Historically, certain manufacturers of boilers with aluminium heat-exchangers have adopted the position that as British Standard BS 7593:1992 Code of practice for treatment of water in domestic hot water central heating systems prohibited the use of softened water in systems with aluminium, it is still unsafe to do so and claim any breach invalidates boiler warranty. (Interestingly, they make no comment on the suitability of boilers in areas of the country where the water is partially softened by the local water utility!). Other manufacturers, who use the same grades of aluminium in their products, have held the position for some time that there is no evidence of increased risk with artificially softened water. The UKWTA has written to all boiler manufacturers in an attempt to seek clarity. For consumers wishing to use water softeners, the UKWTA recommends only boilers with aluminium heat-exchangers from MTS-Ariston. Consumers should approach manufacturers direct for confirmation of suitability of boilers with stainless steel heat-exchangers.

In full (advice may change in future perhaps) http://www.ukwta.org/technology-areas/faqs/

For other pipes (accessible) in a house, my grandmother and all her friends at the time, used to follow this regime (link below), for preventative maintenance, with a heavy amount down each plughole followed by hot water. We use it to clean the kitchen washing up bowl of a tide of soap/grease that sometimes builds up from food preparation/disposal (we have dishwasher), and the soda crystals with hot water just eats away the grease/soap tide; miracle stuff imo, and also washes out to main drains after.

http://www.dri-pak.co.uk/bathroom-cleaning-tips/sinks-and-drains.html

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I know nothing about this stuff, but is a magnetite filter likely the best (value for money) first thing to try with clogging problems? Neighbours replaced their entire warm air heating system and water heater a few years ago to a wet system and boiler - not sure what type - on recommendation from a gas engineer. Don't know whether it's a corrosion or limescale issue but they now have an annual cost of £100+ to unclog the system/boiler and wish they'd never changed it. They didn't say anything about a filter or other recommendation so I might mention it to them; an older couple and could do without the hassle. Also a very hard water area so could be about that

Sounds very like limescale. You can get testing kits to see just how high up the 'lime-ometer' your water is. I've seen one used and they can't be very expensive.

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surely water only drops limescale once in the heating system unless you have a leak.

Correct. But the thread is about a combi boiler which heats potable water.

Combis are at risk of scaling up the heat exchanger used for heating tap water, and the recommendation is that only soft water should be supplied for the hot water circuit.

The use of chemically softened water is a bit more problematic for the sealed circuit, because it has different corrosion properties to natural water. For cost reasons, materials like cast iron, or copper, brass, etc. can be used in the sealed heating circuit, whereas the hot water circuit has to be pure stainless steel. The sealed heat circuit should have a corrosion inhibitor added, but this is frequently forgotten, or the wrong inhibitor added, and there are different recommendations for hard and soft water.

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I know nothing about this stuff, but is a magnetite filter likely the best (value for money) first thing to try with clogging problems? Neighbours replaced their entire warm air heating system and water heater a few years ago to a wet system and boiler - not sure what type - on recommendation from a gas engineer. Don't know whether it's a corrosion or limescale issue but they now have an annual cost of £100+ to unclog the system/boiler and wish they'd never changed it. They didn't say anything about a filter or other recommendation so I might mention it to them; an older couple and could do without the hassle. Also a very hard water area so could be about that.

Unfortunately, it depends where the clogging has occurred and what the design of the system is.

Lime scale can be a problem on hot water systems - because they are always being filled with fresh water. The old fashioned hot water tanks had a huge amount of space for limescale to form and not cause trouble - and even if the limescale made the heating less efficient, because the tank stored a lot of heat, you likely wouldn't notice any problems. With modern combi boilers, the water heater is very compact with very little internal space, and because there is no heat storage, any degradation in heat transfer because the heater has started to clog will be immediately noticeable.

Central heating systems can sludge up because the radiators and pipes "rust" on the inside, producing a sludge which can clog up the heat exchangers in modern boilers. The sludge is magnetic (it's a material called magnetite), so if you put a big magnet on the pipe going into the boiler from the radiators, all, the sludge will stick to the magnet and not find its way into the boiler. Normally, a specially designed filter with integral magnets is used, as this will trap the sludge where it won't clog up pipes. The filter just needs replacing or washing out every few years.

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Unfortunately, it depends where the clogging has occurred and what the design of the system is...

Thanks and to juvenal. Apparently the local water is '141mg/l calcium & 353mg/l total hardness' which is high, so I'll mention it all to them.

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Lowering the flow temperature will slow this. If you radiators burn flesh then your water is too hot,

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Humans have such short memories. Combis were designed during a run of very temperate winters over 15 years or so. New technology is too many times designed for perfect environments..

.

.

Nothing to do with lime scale but reminds me of this in the past..

https://www.avforums.com/threads/frozen-combi-boiler-condensate-pipe-anyone-else.1168662/

Dunno about the 15 years ago. My brother in law bought a flat just over 25 years ago. It had a new combi, failed in the first year.

Incidentally, said flat was a two bed conversion in Markhouse Road in Walthamstow. 50 something thousand.

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Lowering the flow temperature will slow this. If you radiators burn flesh then your water is too hot,

Agree with this try and keep it at about 60 degrees. Above 65 really encourages limescale deposition.

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Sounds very like limescale. You can get testing kits to see just how high up the 'lime-ometer' your water is. I've seen one used and they can't be very expensive.

Get a basic TDS (Total Dissolved Solids Meter) which will give you a reasonable estimate of water hardness as Calcium will make the bulk of the dissolved solids.

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Dunno about the 15 years ago. My brother in law bought a flat just over 25 years ago. It had a new combi, failed in the first year.

Incidentally, said flat was a two bed conversion in Markhouse Road in Walthamstow. 50 something thousand.

Combis are basically a sh1t idea. Much better off with a well insulated cylinder (with the added benefit of an immersion for back up) and 12-18KW Condensing Boiler than a 35-40KW Combi.

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