Hot Water Heating Pipe Choice

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Old 01-17-12, 07:37 PM
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Hot Water Heating Pipe Choice

Hello Everyone!
What's the best type of pipe to use for supplying hot water to cast iron rads I'll be installing? The rads will be delivering about 17K btu/hr of heat, so I know 3/4" diameter will work. The installation needs to sneak through some floor joists and wall studs, working its way up two storeys to the level where the rads are. This is why I need a flexible pipe, and I was planning to use some 3/4" Kitec I have on hand. But since leaks would be a disaster here, and Kitec fittings have proven to break down due to dezincification, I'm not crazy about using the Kitec.

What about using 3/4" rigid copper pipe where I can, then switching to 3/4" flexible where I need to? Is copper up to the this job long term? I will need to put in a couple of elbows, so I'm concerned about the formation of pinhole leaks from the erosion of the copper by the hot water over time. I know this happens all the time in the DHW pipes in high rises.

So what's the best pipe to use in this situation?

Thanks a lot!

Steve
 
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Old 01-17-12, 08:02 PM
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What about using 3/4" rigid copper pipe where I can, then switching to 3/4" flexible where I need to?
Do you have to use the Kitec fittings? Isn't there an alternative that will work with the tubing you already have? Why not go with a different manf of tubing and fittings?

You need to be careful not to damage the tubing when pulling through walls and such... you could do as you propose, but it's gonna get pricey with all them copper to pex adapters and such...

Is copper up to the this job long term?
Yes.

I will need to put in a couple of elbows, so I'm concerned about the formation of pinhole leaks from the erosion of the copper by the hot water over time. I know this happens all the time in the DHW pipes in high rises.
Use the 'long sweep' elbows where possible. They have a bigger radius and less resistance to flow.


image courtesy delafleur.com

I think the majority of problems with pinholes in copper piping has been forensically found to be from improper prep of the pipes before attaching the fittings. Pipes must be REAMED and DE-BURRED, inside and outside, after cutting. It has been found that these burrs and ridges on the inside of the pipes is responsible for forming high velocity 'eddy currents' that do the dirty work.

Flow velocity plays a big part also... heating systems rarely (and should be designed NOT to) flow more than 4 fps. This is pretty slow... as opposed to domestic supply... which can flow more water for a given pipe size. Given the occupancy, high rise piping may be subject to nearly 24 hour flow... at high velocity... and the piping will wear out faster.
 
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Old 01-17-12, 08:06 PM
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I think it will be much more challenging than one might think to pull 3/4" Pex-Al-Pex up three floors without damaging it.

If you DO go with copper, make sure to design such that the pipes have room to expand and contract! Don't make the holes too small!
 
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Old 01-18-12, 09:20 AM
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Thanks for your great answers!

I've looked but have never found alternatives to Kitec fittings. The precise size of the pipe is proprietary, and nobody wants to do anything with Kitec stuff because of a lawsuit about fitting failure.

Would you rate PEX pipe as reliable as copper? What brand do you like the best?

Thanks again,

Steve
 
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