Gas pressure problems, use of MDPE pipe outside?

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Brian99

Hi,

I've just had a new combi boiler fitted in my bungalow (37kW) and the existing 22mm pipe (routed through the loft) is not good enough to maintain the pressure and support the gas flow (the many elbows don't help here and the loft is now converted so cant gain access easily!). Gas meter is outside on gable end.

My only option seems to be to run an external 28m pipe round the outside from the meter position to the boiler (approx 20m) but I do not like idea of an external copper pipe on grounds of electrical safety, asthetics and the very real threat of copper theft.

So, my question is, can I lay an underground MDPE plastic pipe and have this made off onto the meter and boiler? What joints are required and can MDPE be brought into the hosue? My plumber suggests plastic cnnot be used, but as its all UG I can't see why not. :icon12:

Incidentally, the gas board were called in as the presure at the meter was also way too low and they have instaled a biger plastic pipe in place of the not so old plastic pipe. They were prompt though.

Thanks.
 
whats wrong with copper outside?

dont think you can use any plastic after meter, must be metal
 
Hi,

Thanks for your interest.

Besides the fact that copper theft is rife, the wiring regs do not allow earth bonding to be taken outside a building if on a PME supply. As a copper pipe would be bonded inside, the 20m of exposed copper pipe back to the meter would present an electrical touch potential hazard in the event of a neutral fault. I know its done, but its not always safe and besides that 20m of copper running along the building will look awful. Far safer to burry it, hence my question about using plastic, just like the incoming service.
 
Plastic can be used

You will have to have someone with a commercial ticket thou. I think you will def exceed a Dom ticket for installation

It will have to be of the yellow mdpe. And will need to be installed to the regs, of which there are many.
 
The answer is fairly simple if you are gas qualified and have access to a G1. I also think that if your plumber is gas qualified & used the pipe sizing given in the G1 they would have told you prior to the installation of the new 37kw boiler that a 22mm run of "approx 20m" was insufficient. Also, By giving you the answers to the questions you have asked & the fact that you seem to intend to carry out this work yourself would mean as a Gas Safe Registered engineer, I would be in contravention of the regulations & liable to prosecution. My advice is simpler still.. Get a Gas Safe Registered engineer.
 
It would appear you are suggesting I shouldn't have had a 37kW boiler fitted? The gas pressure problem was always a possibility and now its here a solution is sought. I am not Gas Safe Registered and do not intend to touch or alter any gas connections and will employ a gas safe registered person to do this (preferably the plumber who installed the boiler). However, I would like to explore the options with open minded experts before committing to one solution or another and discuss the relative technical constraints. I thought that was the purpose of forums such as this?

By the way, how many copper pipes have you left exposed outside that are connected to internal house bonding on a PME service? I don't want you to worry about it and I'm quite happy to share my concerns without fear of prosecution.
 
I guess you was told gas supply was inadequate but you still went ahead with it did not want to spend the money I guess well your plumber should not of installed the boiler with out upgrading the gas supply great plumber I'd love him to work on my house lol NOT
 
No, there's nothing wrong with having a 37kw boiler fitted but as i said in the previous post the correct sizing for the pipework & the materials to be used should have been carried out PRE installation of the boiler & your plumber (if he is GSR) should have done this simple calculation. The gas pressure problem wasn't so much a possibility but rather a guaranteed fact & a GSR plumber would have known this straight away.

I'd suggest you give the plumber who installed the boiler a call & firstly verify his Gas Safe Registration & then go over what you want doing. Failing that, the Gas Safe Register website has a find a registered engineer page where you can input your postcode & a list of engineers in your area who are qualified to carry out this work will be happy to help you.
 
for a 20m run of external pipework then going into a bungalow, i would be running 32mm mdpe, has your engineer not checked his pipe sizing?( just saying cause i had to run a external MDPE run with a engineer about 2 weeks ago and we run 32mm and it was about a 18m run.
 
Brian99 said:
Hi,

Thanks for your interest.

Besides the fact that copper theft is rife, the wiring regs do not allow earth bonding to be taken outside a building if on a PME supply. As a copper pipe would be bonded inside, the 20m of exposed copper pipe back to the meter would present an electrical touch potential hazard in the event of a neutral fault. I know its done, but its not always safe and besides that 20m of copper running along the building will look awful. Far safer to burry it, hence my question about using plastic, just like the incoming service.
Click to expand...

gas pipes have main bonding and you say this cannot be run then outside? whats PME system in simple terms and how do we spot it
 
What about the numerous earth bonding cables taken outside and bonded within the meter box or is that not PME SUPPLY ?
 
you can bond inside the meter box right?

pme = protective multiple earthing and its the most common used today. I have never read that the position of the bonding is different from one earting system to another, but its been a while since i opened the book.

normally its within 600mm of the meter or can be on entry into the building if the box is external or in the ground. Its unlikely in any event that the position of the bonding clamp be a huge factor in the safety of the installation especially with rcd's.

where is the exsisting bonding?
 
as they must be bonded anyway can anyone tell me what difference it makes to have the copper pipe run outside?
 
I cant see it either, if it has been bonded inside what difference is it then to run on an outside wall as it would be to run up an hallway wall where a child could touch??
 
Would I be right in saying that it has to be bonded after the pipe enters the dwelling to prevent 'perceived shocks'

If it was to be bonded outside. There's is a possibility that any stray voltage could be picked up by someone outside the property and receive a shock. If it is bonded inside there is more chance the stray voltage would be picked up by the bond

Also bonding inside reduces the chance of corrosion of the bond
 
Brian99, where abouts in the wiring regs does it say you cannot bond external on a PME system?
 
@ Simonjohns, no, the gas pipe has to be bonded within 600mm of the meter to the point of entry into the building. So if possible it can be bonded in the meter box or on any exposed pipework within 600mm of the meter or at the nearest point where it has entered the property within 600mm of the meter box.
 
mikimac said:
It doesn't :bucktooth:
Click to expand...

ive never heard of this and i dont see the issue anyway, is he getting mixed up with were the boding is as opposed to where the pipe runs?
if you read his post he has kindly agreed to discuss this with us without fear of prosecution
 
Halesowen1 said:
Must be a huge bungalow to require a 37kw boiler.
Click to expand...

and an incredible amount of bonding required

there is no way that a bungalow unless greater than 8 bedrooms (even then?) would require 37kw for heating so it must be for hot water, begs the question why not fit unveneted?
 
Last edited by a moderator:
I am looking at the gas supply, a huge run of 22mm to feed a gas thirsty 37kw boiler. Never stood a chance, I have seen 30KW boilers drop 3mb working pressure with 6m of 28mm in a 20m run.
Problem is this is a huge problem in our trade but many engineers dont have a clue how to check working pressures and gas rates etc, and many more cannot be bothered.
I have done a lot of inspecting and auditing in my time and half the boilers out there have more than 1mb drop in working pressure.
 
i have spoke to people who think there should be a 1mb drop, not that it is the max permissable!!!!!!!!

to be fair, in many cases you get away with it, if working pressure 23mb at meter and burner pressure needs to be 18mb you can get away with 5mb drop

i know the incoming could drop and it shouldnt be allowed but tis one of the reasons many ignore it
 
You wont get away with it at any of my local councils nor on Warmfront scheme, if its got more than 1mb drop then you upgrade the gas.
 
how many inspectors check your pressure drop across a system and on how many installations? you said people wont get away with it, but they do
 
What I meant was fitters dont get away with it on any contracts I am on, we have every job inspected by our own company and then by the initial company themselves.
But the difference is our work is surveyed properly in the first place, if you know what problems wil arise then you can rectify before it does, hence 28mm pipe on most of our jobs.
Its that initial survey that counts a lot I reckon, if you have the parts there and the knowledge that your work is gonna be checked twice, then believe me you do a good job and make sure its to ALL reg's.
I used to subby to a company doing all there surveys and inspections, I saw at least a dozen teams sacked in 12 months, I would put down x amount of 28mm gas due to boiler, pipe run and other appliances. Only to find that on the inspection after the work had been completed there was a 3mb drop on working pressure and no 28mm fitted, it had all been scrapped. Fitters reckoned it didnt need it when I asked so they were made to go back buy the 28mm themselves, fit it in there own time and when it was done, sack them. Poor workmanship is only going to lead to loosing contracts.
 
Halesowen1 said:
You wont get away with it at any of my local councils nor on Warmfront scheme, if its got more than 1mb drop then you upgrade the gas.
Click to expand...

If you had seen the warmfront install at my mothers house then more than a 1mb drop would be the least of my concerns. The fact i had to repipe 75% of the heating system, the condense, blow off, re make 50% of the rad tails with enough ptfe, alter flue gradient......... infact it would be easier to list the things that was done correctly..... cant think of any thing! :( LOL
 
Halesowen1 said:
What I meant was fitters dont get away with it on any contracts I am on, we have every job inspected by our own company and then by the initial company themselves.
But the difference is our work is surveyed properly in the first place, if you know what problems wil arise then you can rectify before it does, hence 28mm pipe on most of our jobs.
Its that initial survey that counts a lot I reckon, if you have the parts there and the knowledge that your work is gonna be checked twice, then believe me you do a good job and make sure its to ALL reg's.
I used to subby to a company doing all there surveys and inspections, I saw at least a dozen teams sacked in 12 months, I would put down x amount of 28mm gas due to boiler, pipe run and other appliances. Only to find that on the inspection after the work had been completed there was a 3mb drop on working pressure and no 28mm fitted, it had all been scrapped. Fitters reckoned it didnt need it when I asked so they were made to go back buy the 28mm themselves, fit it in there own time and when it was done, sack them. Poor workmanship is only going to lead to loosing contracts.
Click to expand...

done much installing yourself? your talking about sacking decent men here, who ve went back to put things right and then you sacked them? you could end up with a sore face treating men like that. you would if you tried that up here anyway.
Any idea how much the fitters are getting per system ?
just had an agency send me the prices they re offering for contract work with a national utility co. (not BG)
additional pipe - £7/3m copper LOL , thats alright if you ve got miles of straight runs , but when your working in occupied houses, moving furniture,lifting carpets, floorboards, checking joists, forming crossovers cutting in tees, tieing in existing branches, you can see where i m going here, £7 a length is taking the hit or a miss
pay fitters decent money, instead of peanuts, and the quality of the work will rise.

there s 4 man squads doing full systems in a day up here,up to 10 rads all copper, 15mm to rads, combi, gas upgrade. 2 fitters , a joiner , and a labourer . they re getting £450 a system , £150 ea fitter, £100 joiner and £50 labourer . sounds allright but its head down , backside up from 7.30 in morn till 7,8 or 9 at night, with up to an hour and half travelling each way. fitters are knocking their pans in for a £10 an hour , can see whythe gas upgrade gets swerved and the buckshee copper yadded :) , the squads don t get the scrap cylinders , fat cats even want that now.
 
Brian99 said:
It would appear you are suggesting I shouldn't have had a 37kW boiler fitted? The gas pressure problem was always a possibility and now its here a solution is sought. I am not Gas Safe Registered and do not intend to touch or alter any gas connections and will employ a gas safe registered person to do this (preferably the plumber who installed the boiler). However, I would like to explore the options with open minded experts before committing to one solution or another and discuss the relative technical constraints. I thought that was the purpose of forums such as this?

By the way, how many copper pipes have you left exposed outside that are connected to internal house bonding on a PME service? I don't want you to worry about it and I'm quite happy to share my concerns without fear of prosecution.
Click to expand...

Couldn't agree with you more Brian99, this is a forum and raising questions are what they are all about (to me atleast.) Sadly there are alot of sad insecure people on this forum who wish to instantly jump down your throat.
However I would be concerned by who installed your boiler, If upsizing to a 37kw boiler. As a GSR installer the first thought you would have is pipe sizing! Although PE pipe-work is possible, would it not be easier/quicker to re-route internally and up-size. Any good GSR fitter/installer could do some calcs based on distance, fittings and output. Factory sheathed copper pipe is permitted buried in soil as is steel pipe, PE pipe and trac pipe providing they are buried atleast 375mm deep. Whatever happens there will be disruption.
Good Luck.
 
talking to a worcester engineer a while back, they re happy with min 14.5 WP on a Greenstar CDi (gas valve test point) as long as GR is within tolerances, any lower and they ll shut if off. something about the effect off the fan pulling the gas through. WP aint as important as a conventional boiler that need positive pressure to push the gas through.

worked on council sites where they ve pulled up fitters for flue terminals that are 295 from an opening, made firms take out 3/4" tracpipe and replace with 1" even though there was only 2-2.5 drop and GR was spot on. no other gas appliances in the properties. school boy errors by the fitter but a bit over the top imo even for new builds.

refurbs and grant aided jobs in occupied house are a bit different. knowing the theory and having a gas safe card and clipboard is cool but you can t buy practical experience.
 
< 0.004 = :-) said:
done much installing yourself? your talking about sacking decent men here, who ve went back to put things right and then you sacked them? you could end up with a sore face treating men like that. you would if you tried that up here anyway.
Any idea how much the fitters are getting per system ?
just had an agency send me the prices they re offering for contract work with a national utility co. (not BG)
additional pipe - £7/3m copper LOL , thats alright if you ve got miles of straight runs , but when your working in occupied houses, moving furniture,lifting carpets, floorboards, checking joists, forming crossovers cutting in tees, tieing in existing branches, you can see where i m going here, £7 a length is taking the hit or a miss
pay fitters decent money, instead of peanuts, and the quality of the work will rise.

there s 4 man squads doing full systems in a day up here,up to 10 rads all copper, 15mm to rads, combi, gas upgrade. 2 fitters , a joiner , and a labourer . they re getting £450 a system , £150 ea fitter, £100 joiner and £50 labourer . sounds allright but its head down , backside up from 7.30 in morn till 7,8 or 9 at night, with up to an hour and half travelling each way. fitters are knocking their pans in for a £10 an hour , can see whythe gas upgrade gets swerved and the buckshee copper yadded :) , the squads don t get the scrap cylinders , fat cats even want that now.
Click to expand...

I dont sack them, I was only inspecting there work. But the problem is, if they are leaving these problems and blatantly taking the mickey out of the company by tatting the copper in they have been given to upgrade the gas. I dont think the company are doing any wrong, and they aint good fitters if they are not doing there jobs right are they??
Not working to Gas Regs etc, this means companies lose contarcts, multi million contracts for some too.
If it takes 4 men do a 10 rad system in a day then no wonder they are struggling to make it pay. Most on our contarct are 2 men teams and all do 4 installs a week at least.
But not being nasty here, if a company knows they have good fitters then they pay a bit more, anybody can pay peanuts and get monkeys working for them can't they??
Oh and to answer your first question, I have over 15 years Gas exp mainly Heating installs and 20 years plumbing exp. I have done inspecting and surveying jobs in between and bits of auditing too.
 
< 0.004 = :-) said:
talking to a worcester engineer a while back, they re happy with min 14.5 WP on a Greenstar CDi (gas valve test point) as long as GR is within tolerances, any lower and they ll shut if off. something about the effect off the fan pulling the gas through. WP aint as important as a conventional boiler that need positive pressure to push the gas through.

worked on council sites where they ve pulled up fitters for flue terminals that are 295 from an opening, made firms take out 3/4" tracpipe and replace with 1" even though there was only 2-2.5 drop and GR was spot on. no other gas appliances in the properties. school boy errors by the fitter but a bit over the top imo even for new builds.

refurbs and grant aided jobs in occupied house are a bit different. knowing the theory and having a gas safe card and clipboard is cool but you can t buy practical experience.
Click to expand...


But why do a job thats not to reg's?
295mm is not to reg's and yes its only 5mm but its not right.
2.5mb drop is not allowed, it says 1mb for a reason and Worcester and other companies are handing out leaflets to companies about working pressure drops, they are allowing a bit more now due to gas valves. Think Worcester allow 1mb extra so you are allowed 2mb on them.
But you try telling that to an inspector who only knows the 1mb drop rule.
If you are gonna bend the rules a bit, do it where it aint gonna matter or be seen. Cause the first thing you check is the flue.
 
not sure 5mm is going to make a difference wether pocs from a fan flue enter a building or not, obviously the further away the better. if they re going to enter at 295mm, why wont they enter at 300mm or 305mm. i thought gas regs were there for safety and guidance for engineers, not to give mini hitler jobsworth inspectors a cushy job and power trip.
i know and work to the regs . 2.5mb drop is allowed, and classed as ncs if not affecting safe operation of an appliance.
you must be installing a lot of 35mm copper if your sizing correctly to houses with multi gas appliances and high output combis then.
i explain this to customers who dont want their expensive flooring ripped up to upgrade a gas supply when the new boiler will operate perfectly well and safely with correct GR , on the existing 22mm supply.
 
few weeks since last fitted 1 but sure worcester CDi combi MIs state a WP of 16.5 is ok allowing for drop accross the gas valve, their engineers were informed anything less than 14.5 they have to ar.
BG 330 MIs state 15 minimum , if i mind right. i go with MIs .
 
< 0.004 = :-) said:
few weeks since last fitted 1 but sure worcester CDi combi MIs state a WP of 16.5 is ok allowing for drop accross the gas valve, their engineers were informed anything less than 14.5 they have to ar.
BG 330 MIs state 15 minimum , if i mind right. i go with MIs .
Click to expand...

WB cdi min 18mb in instructions which includes any drop across the gas valve. any install that has more than a 1mb drop is incorrect as per gas regulations, it dont matter what the min value the boiler needs to run correctly. If you have more than a 1mb drop then its wrong, simple.

MI state the min requirements of the applaince, this does not alter the need to correctly size the gas pipework to avoid a drop of more than 1mb.
 
< 0.004 = :-) said:
not sure 5mm is going to make a difference wether pocs from a fan flue enter a building or not, obviously the further away the better. if they re going to enter at 295mm, why wont they enter at 300mm or 305mm. i thought gas regs were there for safety and guidance for engineers, not to give mini hitler jobsworth inspectors a cushy job and power trip.
i know and work to the regs . 2.5mb drop is allowed, and classed as ncs if not affecting safe operation of an appliance.
you must be installing a lot of 35mm copper if your sizing correctly to houses with multi gas appliances and high output combis then.
i explain this to customers who dont want their expensive flooring ripped up to upgrade a gas supply when the new boiler will operate perfectly well and safely with correct GR , on the existing 22mm supply.
Click to expand...

2.5mb drop on a new install is not NCS.

cost of materials or flooring is not a vaild excuse to break the regs.
 
As for 1 day installs, i have yet to see one installed correctly and to the book. if you consider you need atleast 4 hours to commission correctly (cold flush, hot flush after min 2hours, balance etc...) thats why so many engineers have loads of bottles of cleaner on the back of the van. lol
 
we all know the regs state 1mbar drop between meter and appliance. it's outdated though.
if i can prove a premix burner is working to full performance with correct GR/HI , temp rise on DHW, CA values, no affect on safety of any other appliances, as a gas engineer i m happy as larry. if it s not performing to full performance and is undergassed , then it gets upgraded . thats engineering judgement , and no reg is going to tell me a boiler operating perfectly on a 22mm supply is going to work better on a 28mm

suppose yous all always calculate the IV of the pipework for purging as well lol

tamz knows the script , watch out for a TB on coming soon
 
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