Piping question (two 1" lines instead of a single 1.25 line)

[MrEd]

Question for those plumbing experts out there:

My tarm solo60 calls for either a 1.25 or 1.5 inch pipe to go from the tarm to my oil boiler. I priced out 1.25 inch black-iron pipes and materials alone will cost about $600 from my local plumbing supply house. Couldn't find anything bigger than 1" at home depot.

Question is, if I use double 1" pipes it gives me a volume that falls roughly between a 1.25 and a 1.5 inch pipe, and will cost 1/4 as much. Would this work? Any other pitfalls to this? I am picturing coming off the boiler with the 1.5 black iron pipes, into a "T" of some sort, two 1" pipe runs to the boiler where they would be re-joined via a "T" and into the 1.5" pipe again....same thing on the return loop.

Working with 1" pipe will be easier for me, and also opens up the possibility of using 1" pex for the long run (about 50' in either direction).

Opinions?

 

[chuck172]

My Tarm will be 45' from the oil boiler. I bit the bullet and bought 1 1/4 M copper. Very expensive. Look into Pex.

 

[Chris S]

Capacity in cross section is not the same as flow. I studied fluid mechanics in college, but it's been a long time. Bottom line is that there is friction against the edges. My feeling would be that in an equal cross section area, the head loss in 2 pipes will be greater, but I couldn't say how much.

 

[Redox]

I suspect the heat loss will also be greater with 2 smaller lines, the insulation cost will be greater and the chance of a leak will be double. Might want to look into that PEX now...

Chris

 

[bigbobs]

Had no problem obtaining 1-1/4" Black iron pipe and fittings at Home Depot, they also had the best prices and cut and threaded pipe.

 

[MrEd]

My local HD didn't carry it, not even a spot on the shelf for it, but then again it is a smaller-scale HD. Maybe a drive to one of the full-size ones is in order. I suspect the prices will be 1/2 the cost of the local plumbing shop.

 

[WRVERMONT]

Hello,
On a recent installation I used double runs of 1" Pex in order to maintain high flow between boiler and storage/fossil fuel boiler. It worked great. This run was 50ft. Used a total of 200ft of Pex. It takes care of 200,000 Btus/h with no problems. Good luck with your system.

 

[foxt]

Did you do anything fancy to terminate those dual 1" lines? Or just connect them to 1x1x1-1/4 T's on both ends?