Best way to protect pipework buried in Garden , Boiler to House

[verdigrey]

Hi all , I am an Oftec reg engineer , but have not come across this prob before . A customer would like an external oil fired combi boiler fitting about 6 metres from the house . Near to a brick out house . ( it is not possible to have it nearer ) I would like to use 22mm plastic pipe and bury it under the garden . Does anyone know the best way to protect it ? I thought perhaps put it thru 25mm mdpe pipe , foam insulation then some kind of waterproof coating . I have heard that you can get special pipe in pipe for this purpose , but I think it may be expensive .
Any ideas please ?

 

[SafeGasInstall]

what is to be run is this 22 mm ?

 

[SimonJohns]

I would buy some of the stuff that comes in 6" tube. Heavily lagged and well protected

 

[SimonJohns]

http://www.uponor.co.uk/solutions/renewables-and-energy-solutions/pre-insulated-systems.aspx

 

[Best]

The " pipe in pipe " is apparently very expensive. You could duct pipes using 4" sewer or duct pipes. Gutter down pipes can take a 22mm pipe with insulation on it. Use, if you have to,rubber joint fittings or solvent as appropriate. Run straight to house if possible, & through wall below ground, & seal with sand & cement. Ducts at boiler need sealed to stop rodents. I would be careful with wiring install. I wouldn't personally use plastic heating pipes, just copper, & plastic shouldn't be within, I think 2m of boiler.

 

[verdigrey]

Thanks for your replies , I could possibly do it in copper , but there would be a lot of joints . anyway I will think about it , off to work now cheers .

 

[dontknowitall]

If it were me I'd phone OFTEC (or the boiler manufacturer) and lay the blame on them if it didn't work properly (i.e. losing too much heat/too expensive to run).

 

[Joncpi]

Use 22mm speedfit pipe, it will withstand the heat. Lag with armaflex (this is closed cell so wont absorb water) and glue the joints, sand the trench 50mm below pipe and 100mm above. Then if you want a solid protection there are concrete capping slabs that can be laid over the pipe or alternatively I know there are fibre boards that can be laid over electric cables but I dont know if the same thing is available for water pipe. Lastly use a plastic marker tape over that and then refill the trench with excavated material, if soft dig, and compact. If not and it is under a hard landscaped area such as slabs or tarmac then fill the trench with scalpings and compact. If you don't the ground will sink and caused a "trench line". In all cases duct the pipe where it goes down or comes up through concrete. More or less anything in plastic will do for this if rising in speedfit, though MDPE is probably best. If you are rising up in copper then use a larger diameter copper duct or sleeve.

 

[verdigrey]

Thanks Joncpi , That sounds like a good way of doing it , Cheers mate .

 

[dave.ackroyd]

From what I have learnt you have to have it buried between 750 - 1350mm to protect against weather also amour duct the MDPE and lag it too, I know that applies to water not to sure on oil.

 

[Gray0689]

Use ecoflex or flexallen
Or just plastic pipe with armaflex lagging and ducted
Mdpe is not really for heating pipes it's for mains water

 

[Joncpi]

The depth of 750mm to 1350mm is for water supply pipes only. As far as I am aware this does not apply to hot water piping, especially as it is lagged not only to prevent heat loss, but it would also prevent freezing if out of use for any reason. However I would have thought around 500mm of cover would be sufficient in order to reduce possiblity of accidental damage.

 

[fuzzy]

duct it if possible then lag it

 

[dontknowitall]

Alternatively do what most people do: lay it on the ground then kick some gravel over it to prevent an eyesore.

 

[Gray0689]

Lag then duct

 

[verdigrey]

Thanks Guys , we will probably start the job tomorrow , The weather forecast is good after today , Cheers .