pex size

heatboy

.....on load, distance, pump size, piping scheme, etc. I have used 5/8", 1/2" and 3/8" with no issues.

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Scott M_3

pex size

I will be replacing my hot water boiler this summer and have decided to add baseboard heat to my basement that I will install myself and have the plumber connect to the new boiler on its own zone. I will be using pex with an oxygen barrier but I am not sure if I should use 1/2 inch or 3/4 pex. Also wondering if I should use the pex with the aluminum built in to make the bends easier. Thanks

Lunatic Fringe

use 3/4\"

The baseboard will be 3/4" and the hydraulics will work better including less head

Andrew Hagen

Size

It depends on the heat loss and amount of baseboard on each loop, but generally 3/4" is adequate. I would use pex-al-pex. Still make sure to use plastic tube isolators anywhere the pex could touch wood in order to eliminate the possibility of expansion noise. As a retrofit in a basement, you will probably have a lot of high spots in the tube. These could trap air, so be sure to have a good air eliminator. I don't know what your plan is for the boiler replacement, but it is worth looking into using a modulating condensing boiler if your fuel is gas.

Unknown

I recommend Pex-AL-Pex to hold shape and expand less with higher water temps.

1/2" or 3/4" depends on the load you are servicing. I don't see a single advantage to 3/4" if you don't need to push that enough flow to warrant it. If it keeps you from upsizing a pump, great, but if not, there is no point.