Don't worry this is not my latest DIY project! This is one for a heating engineer only. I have convinced my parents that before I fit a new kitchen it will be a good idea to have the 30 year old boiler replaced as costs a fortune to run and there is obvious safety implications long term.
My parents want another gravity boiler as the water tank etc is already in place, the problem is I know many people need new gas pipes when having a new boiler fitted. The gas pipe is 25mm which I believe according the regulations is ok, the problem is it must be about 50 feet long in terms of the root it takes to the boiler, and I assume the longer the pipe the thicker it needs to be to take a certain amount of pressure required by the boiler.
Is there a good chance this pipe will need to be replaced? The problem is if it does it goes under the upstairs floorboards as the kitchen floor is concrete, but it will be a massive massive job to empty one one of the rooms upstairs to gain access to the floorboards.
So what is this pipe at 25mm likely to need replacing?
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Here's how to calculate the required pipe size(s). www.arca53.dsl.pipex.com/index_files/gas4.htm
>> ........ I assume the longer the pipe the thicker it needs to be to take a certain amount of pressure required by the boiler.
I don't think that's the case.
Last edited by: L'escargot on Sun 1 Sep 13 at 07:18
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No need for new pipe to take same route as old one. Our neighbour, in house identical to ours, replaced OEM Baxi with a modern condensing jobbie. Installer ran new pipe round exterior of house rather than faf with carpets, boards and suspended concrete indoors.
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>> the problem is I know many people need new gas pipes when having a new boiler fitted.
>>
Really ?
>>Is there a good chance this pipe will need to be replaced?
A short length of pipe to mate up to the new boiler but else , IMO, beyond that I suspect it would be a guy boosting the job.
More than a few years ago my C/H failed to work at the start of autumn.
My brain switched off and a called a recommended plumber.
" sucks teeth, old cylinder and boiler needs replacing etc etc £2K+ " all those years ago.
Yeh! Yeh! Brain back in gear. Nudge header tank ball valve and all started working again.
As a precaution a new washer for a few pennies.
Same cylinder still working OK.
Beware out there. Google is your friend.
I have only known of one gas pipe needing replacing and that was in a seven year old house.
Rubbish plumber caused it to fail.
I have removed gas pipe from my 80 year old house and it looked good for 180 years.
Of course when having any pipe extension, appliance fitted I always get a Gas Safe guy to do it.
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I can't help on those size of the gas pip Rattle, other than to say ours is 22mm and did not need replacing when the boiler was changed a few years ago.
Are you sure about needing the replacement to be a gravity system though? I thought all boilers would have a pumped hot water circuit by now! Do you just mean you want to retain the hot water cylinder rather than go down the combi route? I think you need what's called a system boiler? If you do want to keep the cylinder (good move in my book, if you have space) have you considered a mains pressure system - you'll great a great shower if you do :-)
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>> assume the longer the pipe the thicker it needs to be to take a
>> certain amount of pressure required by the boiler.
You assume wrong. Does that help? ;-)
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>>I have convinced my parents that before I fit a new kitchen it will be a good idea to have the 30 year old boiler replaced as costs a fortune to run and there is obvious safety implications long term.
>>
What safety implications?
By coincidence...
" I would rather keep my 44 year old Potterton Diplomat 75% efficiency than switch to an electronically dependant condensing boiler with an alleged efficiency of 85 % but would have had to be replaced or extensively repaired nine times within that time frame"
says Jeff Howell the builder in todays Telegraph.
I read that condensing boilers have a life of about 5 years.
I ensured when I replaced my large floor standing boiler that the new boiler had a an iron heat exchanger.
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The reason is I will be gutting the kitchen probably after Christmas, the boiler is in the kitchen and I assume replacing it will be a messy job which will require redecorating. The boiler is a Glowwarm Space Saver MK2 which was installed by British Gas in 1984. I meant a conventional boiler with the cold water tank in the loft, and the hot water tank upstairs.
The boiler is almost 30 years but I always assumed the Glowwarm was just a bog standard domestic boiler and as such is now on borrowed time, or were boilers made in 1984 really so much better than current ones?
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I'm no DIY man so take any suggestions with a large pinch.
Looking at it logically, that old boiler ..;) might carry on for many years yet, if it costs £2k to replace and a new one saves £200 a year it'll only pay for itself in 10 years and will be scrap by then...
Why not gut the kitchen and refit but when you do so make sure there is good easy access to the boiler and putting right after the boiler really needs replacing at some point in the distant future is an easy job?
Is this new boiler syndrome to save money a similar quandry to people spending £10K on a car that does 10mpg more than their present perfectly good car.
Last edited by: gordonbennet on Sun 1 Sep 13 at 10:03
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I think the fear of it is breaking down and needing a new one which would then take weeks to have fitted. We have just had new double glazing fitted to the back of the house so that should help with heating costs.
I know the seals on the boiler need replacing and it will need a good service, but I suppose even that is only going to cost £200 rather than £2k for a new one. There is other gas work that I think needs doing though, there is an old lead pipe which is not attached to any joists but just sitting freely which goes to the old unused gas fire points, this pipe is still live but not doing anything so it needs disconnecting from the tank.
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You can buy a decent gas boiler for £650 - £700 + the dreaded vat. A decent gas fitter to do just that. 'Should' be a days work, say £200 - £250 quid. BUT....if it's still a runner I'd leave well alone. £200.00 for a service is way too much.
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>> I meant a conventional boiler with the cold water tank in the
>> loft, and the hot water tank upstairs.
>>
>> My parents want another gravity boiler as the water tank etc is already in place.
I assume you have a "gravity system" at present? The flow return pipes to the cylinder are usually 28mm / one inch and you do not have fully independent control of C/H and hot water.
If this is so then I would be converting to "pumped primary" even if you keep your existing boiler.
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>> I read that condensing boilers have a life of about 5 years.
They don't. Double that and you are about there.
>> I ensured when I replaced my large floor standing boiler that the new boiler had
>> a an iron heat exchanger.
You wont be able to do that now.
Last edited by: Zero on Sun 1 Sep 13 at 10:08
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>> >> I read that condensing boilers have a life of about 5 years.
>>
>> They don't. Double that and you are about there.
That's still a short life span. I suppose based on that information, a boiler fund should be opened and added to over the next ten years in order to replace the existing one when it croaks.
Why don't they last long? Is it due to the inherent design or just poor materials/build quality?
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>> That's still a short life span. I suppose based on that information, a boiler
>> fund should be opened and added to over the next ten years in order to
>> replace the existing one when it croaks.
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>> Why don't they last long? Is it due to the inherent design or just poor
>> materials/build quality?
They have small volume thin walled heat exchangers, one of the reasons they are more efficient. As such they are very much more prone to heat soak and heat damage. Sediments, corrosion, air, poor water flow all cause hot spots and break down the exchanger. And its its exchanger failures that will render a boiler beyond repair.
All those issues are mostly caused by poor installation, and lack of servicing on the rest of the system.
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The existing 3/4" pipe for the incoming gas is fine Rattle.
All the Housing Assoc properties in my street are undergoing a programme of boiler and CH upgrades, mine was done one day last week. They replaced the 20-year-old boiler with a new combi unit, changed five single radiators for doubles and removed the HW cylinder and header tanks.
The only mess that was left behind was a thin coating of brick dust everywhere, and a few small patches of new plaster in the kitchen and airing cupboard where pipework was added or removed. It's no more than a couple of hours' work to make good, although I'm giving the plaster a few days to dry out thoroughly first.
>> Installer ran new pipe round exterior of house
They said they don't do that here, the pipes get nicked.
Last edited by: Dave_TiD on Sun 1 Sep 13 at 13:35
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>> Why don't they last long? Is it due to the inherent design or just poor
>> materials/build quality?
>>
To an extent it's because people aren't prepared to pay a substantial price to get a high quality long-lasting product. You get what you pay for.
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Nothing last for ever,ten years for a condensing boiler isn't bad.Regular service is important.Our previous boiler Glow Worm had it for twenty five years.
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>> >> Why don't they last long? Is it due to the inherent design or just
>> poor
>> >> materials/build quality?
>> >>
>>
>> To an extent it's because people aren't prepared to pay a substantial price to get
>> a high quality long-lasting product. You get what you pay for.
>>
No, it's because the only way to achieve the stonking efficiency that modern boilers return is to get as much heat into the water as possible in a short cycle time, and to do that the exchanger must both be thin (maximum heat transfer instead of wasting energy heating up the exchanger) and aluminium, which has a far greater thermal conductivity than steel.
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>> So what is this pipe at 25mm likely to need replacing?
Only way to be sure is to ask a trusted gas man.
A lot of boilers being fitted now, especially combis, are a lot more powerful than those they replace and will require more gas volume. This can cause problems such as the boiler sucking gas away from the gas hob and causing the hob flame to go out. It may require larger pipes or pipe/junction relocation to resolve.
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Our old system was taking out boiler plus header tanks and emergen tank out the upstairs landing cupboard.
No pipes replaced our central heating pipes are microbore thirty years old.Radiators same age standard Myson radiators.One of my jobs long time ago was crosswelding radiators.Good payed job as a machinist.Our condensing boiler was fitted five years ago serviced regulary.
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The size of the pipe is related to the length of the run and the demand by the boiler. Gas supply is goverend at the meter to 20mbar, and most boilers will require close to this to operate properly - ie minimal pressure drop in the pipe. The reason many people have to upgrade the supply pipe when fitting a new boiler is the change from stored hot water to combi. The former will typically have a boiler rated at 10 or so kW whereas a combi is rated at 30kW (if you want a half decent HW flow in the winter!). Hence much higher gas demand. Whilst the old boiler was OK on a 15mm supply pipe, the new one will most likely need a 22mm.
Now, if you are just replacing the boiler like for like(*) then the old supply pipe (assuming it's in serviceable condition!) will be OK, but if you upgrade to a combi, or much larger boiler then a new pipe will be needed. I changed our system from a Baxi back boiler to an 18kW wall hung at the other end of the house and had to replace the supply pipe. My calcs showed it was probably OK on 15mm existing for the first half, but the plumber wanted to do it all in 22mm.
* you can't. You have make a very good case for not going to a condensing boiler, and I very much doubt you can get a non pumped primary boiler anymore - so you will need to convert to pumped primary, and condensing operation. Neither is a disaster as it appears your boiler is near a drain for the condensate, and downstairs vs a header tank up stairs in the loft so you will have enough head to run an open vented system with a pumped primary in the boiler. Your plumber might take some convincing though....!!
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Incoming gas pipe and boiler - what size? - L'escargot
