DIY Insulated Duct

Glulam

I am putting my hot water cylinders (DHW & Buffer) in the garage which is approx 8M from the house. I need to make up an insulated duct to carry the 4 pipes ( 2 supply 2 return) between the house and the garage.
This is what plan to do
Cover all 3/4" pipes in armaflex lagging.
Tie them all together using cable ties.
Place them all in a 6" sewer duct and center in the duct.(not sure how???)
Drill some pilot holes in the 6" duct and pump with foam. theres a local insulation crowd who will do it free gratis.

I priced a similar pre-fabricated pipe from heat merchants and its 42/M so its quite expensive!!!

Any ideas for above your suggestions would be welcome

RKQ

Sounds good... but you'd have to experiment with cutting the pipe in half and making sure the foam insulation would fill all voids.

Would using 2 half round pvc gutters push the cost up too much?
Or use yellow drainage pipe - holes already there so you'd see the insulating foam.

Wrap the finished pipe in silage wrap to help water proof it.
I'd dig the trench 300mm deeper than required and fill the bottom with 300mm of pea stone - for drainage - keeping water away from the pipe.

Try this:
Get 4 "qualplex" plastic pipes, bundle them loosly together then at regular intervals place a piece of wood with four holes (shaped like a button), place a piece of foam rubber pipe insulation around each one (separatly) the lengths of pipe insulation will also space the "buttons" equally along the pipes before pulling into the pipe and filling with foam. Don't use rigid sewerpipe, it'll be a nightmare to handle, do as RKQ suggests and use flexible.

If you have enough holes then there should be no problems with voids also the pipe lagging will also insulate as well.

Poor Uncle Tom

Glulam wrote: »

I priced a similar pre-fabricated pipe from heat merchants and its 42/M so its quite expensive!!!

The prefabricated pipe is SPECIFICALLY for jobs like you describe and well worth the extra money to get it right. It should pay for itself in the short term, and it's peace of mind that the job is done right.

Poor Uncle Tom

Poor Uncle Tom wrote: »

The prefabricated pipe is SPECIFICALLY for jobs like you describe and well worth the extra money to get it right. It should pay for itself in the short term, and it's peace of mind that the job is done right.

I have to agree, I have a length of insulated pipe 30m between the house and the garage.

30 metres was just too long to consider anything else!

flocker

You might need to consider a secondary return on you DHW as there will be a long dead leg before the hot water starts flowing.

flocker

flocker wrote: »

You might need to consider a secondary return on you DHW as there will be a long dead leg before the hot water starts flowing.

I have the buffer tank in the garage and a "thermal store" in the house, I also have a recirculating pump to bring instant hot water to the bathroom taps (in hindsight I should have put the airing cupboard nearer the bathroom!) It's halfway between the kitchen & bathroom.