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Insulating hot water pipes,recirculating pump

16 years ago

We'll be building a new house with a slab on grade foundation. It's all on one level. No plumbing fixtures on outside walls. I'm trying to develop the specs for it now and am woefully ignorant about where the pipes go. I understand that all the hot water pipes should be insulated, but does that apply in slab construction??

We'll also have a recirculating pump on the hot water, in an open system.

Are my pipes in the slab or in the walls? And what kind of insulation do I specify? The exterior walls will have Icynene spray foam insulation. All the mechanical systems will be housed in a Mech. Rm. between the house and garage, all attached to the house.

Thanks for any help.

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Comments (5)

jake2007
16 years ago
Hot water pipes in the slab absolutely need to be insulated. Otherwise, you are looking at a cold shower.
davidandkasie
16 years ago
let me tell you about pipes in the slab.

in my area of the country it only gets below freezing a few days a year. most of the cold days have highs in the low 40's and lows in the upper 20's, so not bad at all compared to otehr regions.

from late Nov to late march, the ONLY way you could get hot water in the master bathroom was to leave the diverter set to where the tub spout was flowing some as well. if you turned it full to shower, the water would cool back off within just a couple minutes. even today, with 100 degree temps, my sink will only get hot if both sinks are running or if my wife is taking a shower at the same time. there just is not enough volume of flow to overcome the heat loss in 175' or so of pipe.

YES you want them insulated, and with a recirc they must be FULLY insulated. NO you cannot have them in direct contact with slab either.
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pinktoes
Original Author
16 years ago
Um. So our (copper) supply pipes, and those that return the hot water for recirculating, will be IN the slab yet they cannot be in direct contact with it. So, how are they insulated? I mean, what kind of insulation is it that will fully enclose them from the concrete?

(We're in Atlanta, GA, and I do know about frozen pipes here! It happens.)
davidandkasie
16 years ago
they should be under the slab, i am not sure how exactly they insulate them.
lazypup
16 years ago
Although the pipes are defined as "in the slab" that is a slight misnomer. They can be said to be "in the slab" in the sense that once the slab is poured it would require cutting inot the slab to access the pipes but in actuality the pipes are laid in the subsoil under the slab prior to pouring the slab.

Both the International Residential Code and the Uniform Plumbing code require that whenever a pipe is run through a masonary material the pipe is to be sleeved with a section of sched.40 pipe at least 2 nominal trade sizes larger that the desired pipe, however some local codes will allow pipes stubbing up from underslab to be sleeved with light guage flexible PVC tubing to prevent direct contact between the pipe and masonary material.

The pipes both above and below grade may be insulated with standard foam pipe insulation and in some jurisdictions the foam pipe insulation will be accepted as a sleeve when stubbing up through the slab.

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