anchoring PEX in sand lift

Royboy

under a slab, with the function of 'lifting' the slab up above groundwater, clay, etc.

that's the term used here in n WI, anyway.

Royboy

anchoring PEX in sand lift?

I have a job where the radiant slab design (done by someone else) calls for 1/2" pex tubing to be located in the midst of a substantial insulated sand lift. The design seems good - so I'm not thinking to question it - but I'm trying to figure out how to anchor the tubing.

I could imagine putting down a layer of mesh and zip-tying to it - seems like a relatively expensive option. Or using pex-al-pex (like Wirsbo MultiCor) and figuring it will stay put. But I've never used that stuff and am not sure if I might be creating other headaches (my supplier says most other installers don't like it).

Thoughts - suggestions?

Thanks - Roy

Dave Larsen_2

pex-al-pex

Try the Pex-al-pex! I've installed miles and miles of it............absolutly no complaints!

Royboy

that's encouraging, dave

do you run it off a spool like regular pex? any installation details/practices that would differ from regular pex?

Unknown

gotta ask

Gotta ask this, what's a "sand lift"?

hr

Why not pea gravel

which is 100% compaction without much work? Dry sand is not a very good conductor of heat if you plan on suspending the tube in the middle of a sand layer?

Also it would be better to address any ground water around the exterior of the slab or basement. Any water, especially running water will wick away heat like crazy.

Can't think of any reason you should ever have water under a radiant slab. Other than a good old 25 year flood as in hb's pics

Wouldn't running water take the sand along with it? Gravel allows water to pass through.



hot rod

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gkaske

Sand lift

I will have to agree with Hot Rod. Would like to know design particulars though on the "Insulated sand lift".

sometimes certain aggregates are hard to get in areas with out some trucking involved, so you use whats in the area.

I'm going through this with concrete aggregates at the job I'm running. I can't get a three day break for nothing.

Limestone aggs with their angular surfaces will give a 4000 psi break easy in three days. But the concrete supplier only has natural stone avaliable via there own quarry, you get your breaks but it takes 7 to 14 days.

Not to side track but sometimes the reasoning for doing things is tied to resources that are avaliable at a reasonable cost.

Gordy

RadPro_2

PEX-AL-PEX is great but...

I put in almost 10 miles of PEX-AL-PEX last year. I hope your arent thinking of laying out tube across sand and expecting the tubing's rigidity to keep it in place.

Between the army of concrete workers tromping over the area, and the material screaming down the shoot, you are in for a VERY BAD DAY.

I've seen it all, even when tube is securely fastened to wire mesh, men trip on tube and break ties, concrete coming down the shoot can lift the entire wesh/tube assy if you you dont carefully monitor their work.

I vote for WWF mesh, and metal spin ties every 3 ft! Once the concrete starts flowin, those guys dont stop for anything!

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Royboy

actually I WAS hoping

to have the tubing's rigidity keep it in place, not in the face of the concrete pour but for the placement of the next foot of sand that will be hand dumped on top of the tubing and then compacted and the slab poured on top of that.

so my question to those of you with pex-al-pex experience is whther this is realistic or not. will the tubing stay put enough to wheel sand in over it (with a garden cart, I'm told) for another foot of fill.

as I said, I'm not the designer on this. the plan is that the insulated sand bed will be charged with a hydronic solar system starting in late summer/early fall and there will also be a boiler connected to the sand bed and a few stategically located baseboards and panel radiators as a backup and quick response option.

I will be connecting with the designer to see if he has some ideas about the best tubing/fastening option to use but thought I'd try to see what you all think, too.

thanks again - Roy

hr

I doubt

that it would stay put until the sand is spread over it. Straight runs lie pretty well but the bends at the loop ends tend to want to rise up.

Regardless of who the designer is, I think you have the right to question the sand bed. Run some calcs to see if and how much you can transfer through the sand. Keep in mind some may get pushed down deeper than you plan.

Also warm sand tends to attract all sorts of insects, ants, etc.

Install some glass covering so you can witness the largest and happiest ant farm in you area

hot rod

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jp_2

holey Cow

you are putting a FOOT of sand over the PEX? yikes, what is the designer trying to do? heat storage?

Royboy

yes, exactly

the idea is to be able to charge up a large (sand) mass with solar heat before the serious heating season begins. my impression is that the designer has done quite a few installs in this manner and has refined the design to one that works quite well. I'm quite intrigued to work on it.

and can post more detail here as this moves along, if anyone's interested.

Paul_59

rebar

Lay 20' lengths of rebar on sand and tie pipe to it.