Pex tubing install. Help

[Jay430]

Okay, so I'm getting ready to have the pad and stub wall poured here in the next week or so, and after the footings are poured, and before the floor is poured, I'm going to lay out my tubing that will be coming up in an interior wall.

My question is very simple. What do's and dont's could you guys give to someone who's never layed out a single foot of pex tubing in their life. It will be a few months before I even get to actually installing the rest of the system, but need to make sure everything in, and coming out of the floor is correct.

 

[Highbeam]

It's not that hard. For the most efficient use of tube and most efficient use of energy you could pay somebody to do the design work for you. Do you already have a plan or are you seriously going into this blind and expecting good results in one week?

Look at examples on this site. Visit vendors websites to learn the rules of thumb. Since this is not a house it doesn't need to be as perfect.

 

[sands35]

Grab a piece of graph paper and lay-out a scale drawing of your floor.

Space the tube at 12" on centers and lay out different options.

You want your loops to be as close to the same length as possible. Keep in mind that PEX comes in defined lengths. 250' was what I could get locally. Longer lengths if you order on-line.

My garage is 26" x 32" and it took 4 loops about 190' each.

250' lengths turned out perfect as I simple layed out the excess on the lawn and adjusted the loops until the long ends matched in length. No measuring tubes required.

Build a frame with a ~2x4' plywood wall overhanging the floor. It will need to cantelever out over the to-be-poured floor. You'll want the tubes to come out of the floor ~3 inches or so from the finished interior surface of the wall. Use Schedule-40 90* electrical elbows to make the turn up the wall from the floor. Those will protect the PEX during the concrete pour and dress the PEX tube nicely. Attach the tubes to the plywood wall and dress them to they look neat.

Do your pressure check. I just daisy chained them together end to end with 90* elbows. Filled with compressed air and let it sit. The only leaks I had where on the fill manifold that i built.

MAKE SURE YOU USE OXYGEN BARRIER or Pex-AL-Pex tube.

It is pretty simple if your garage is symmetric with the heating unit on the center of one wall. If not, then you'll need to get creative with your layout to make sure all the loops are the same length.

There are flow meters on the manifold that I have. They required zero adjustment to have even flow. I borrowed a FLIR from work and the floor was consistent in temperature for the different loops.

I did leave some room for bolting down a lift and an air compressor. Basically just brought the tubes together to move the tubes away from where the lift will bolt down.

I rolled the pex out and stapled it down every 8' or so and got it close to right, then adjusted a few loops to make them the same length. Then stapled them down every 3-4'.

 

[rburke65]

When I ordered my pex on line, i needed 1800' and I thought I was going to get 6 rolls 300' long but what I got was 2 rolls 900' long. The tubing had footage marks on it ....and not 1, through 900'...... It was more l Ike....265,677 to 266,577. Made sure you knew where the next 300' make was before ya cut! So that was one surprise. Laid it out in the sun to soften. I tied my pex to the wire mesh so it was easier to follow the lay out plan. The outer perimeter runs were a little closer together to combat heat loss at the outer edge. There is a ton of info on here....do a search. Good luck. Ask if ya don't know. And insulate the he'll out of it!

 

[eriederie]

1.5 inch Styrofoam sheeting on bottom and sides duct tape the joints then put vapour barrier on top lay down wire mesh and ty-wrap down

 

[brewchief]

Lay it out so your tubes don't cross each other, keep lengths the same and 300' or less for 1/2", use barrier tubing.

300 foot rolls are easier to handle then 900 foot rolls, doubly so if you don't have an unwinder for the big rolls to help handle them.

Label each tube as to supply/return and loop#.

Take pics, if you leave an area clear for a lift(I would if it's even a remote chance) then write down clear measurements someplace that can't get thrown away( A piece of old cardboard is not ideal, ask me how I know).

Have pressure on it during the concrete pour, I like to see 100 psi.

Stapling down or tying to mesh?

 

[Jay430]

Thanks guys, alot of good advice there. I live up here in western Montana, so my primary heating source is going to be wood. I was going to use the in floor as more of a comfort thing and extra source when it gets -20 in the winter.
I never thought about buying the smaller rolls so their easier to handle and for sure will be doing that. I will be tying it down to the re-bar. Going to do the spray in cor-bond insulation under the pad. And like the idea of using the electrical elbow to bring it up out of the pad.
It will be 1/2" ox-barrier, and I was wondering what would be the best way to pressure test it, and leave it pressurized during the pour. Should I go ahead and install the manifold with a pressure gauge on it?
The side that I will be heating will be 28x37 and will have a two post in it but that is all ready planned out in the pour with thicker floor and more re-bar, so avoiding it will be easy.
I've been reading alot of post on here and seeing what other people have done and listening to what others have done and feel pretty confident in doing it myself, plus I live in a small town and therefore know a few contractors personally that I ask for advice from, including the one doing my mud work. I simply just didn't want to pay someone to do it if I could, and irritate them with 1000 question day during their busiest time of the year. So I really value your guys input.

 

[Highbeam]

I did not want to put manifolds on for a pressure test and also to protect them from damage. I simply **** connected all the loops to each other so that I had one really long pex pipe and then used a typical water pressure tester kit to pump it up with air to 100 psi. Left it there for a long time.

 

[sands35]

I did what highbeam did to pressure test it.

My garage was the 1st time I did it too. I'm pretty handy, but the job was no harder than a basic plumbing job. You'll just need some PEX crimping tools.

I made a manifold out of hardware store parts to put a pressure gauge and a Schrader valve. You can buy one ready make for 2x the cost of a DIY part. Not like it's that expensive anyway.

28x37 works out to 1036 ft^2, which would be 5 loops of about 207 ft each. 4 loops would be about 250 ft. (not counting the ~5-10 feet you need coming out of the slab.)

The barrier pex I bought at Menards was in 250 ft rolls, which I assume is somewhat common. http://www.pexuniverse.com/ (no affiliation) sells it in 300 ft rolls. The recommendations I've read suggest keeping loops to under 250-300 ft for 1/2 tube.

 

[Beefbuzz]

Search google and download the trial version of loopcad. This will make the layout super quick. There are a few videos on the loopcad site that show exactly how to do a layout. So an hour of videos and 10mins of layout and print to PDF.

Take the PDF via thumb drive and get a nice big color print out at kinkos or somewhere. I took the extra step of laminating it at the copy shop too. This was a lifesaver as it ended up raining the whole weekend while I did the layout myself. Also, it was windy and the extra big layout I slid under the tubing but on top of the wire of a just completed zone to hold it while I worked. If you can let the tubing lay out in the sun, warmer tubing bends easier.

If you are doing it yourself, I highly recommend the wire mesh clips. I got 5 packs of 100 for 7 zones at about 300ft/zone and it was perfect. For any really extra difficult spots I added some zip ties. Your fingers will get tired after a while so I used a 8" cresent wrench to snap in the wire mesh clips. Protip: you can easily undo a clip if needed...you flip it over and use your two thumbs and push while turning in the unlock direction.

I had to have mine inspected as I did it as part of a house build and the inspector required 100psi. I purchased all of my materials from pexsupply.com

 

[Jackfre]

I always made a manifold for the supply and return and pressure tested that way. I would also add a few drops of oil of Wintergreen or peppermint. That way if the meatheads doing the pour cut the tubing there was no question of it and I could get in and repair immediately. These were on a couple warehouse size jobs a long time ago. I only had one cut, but I'm glad I had the press and wintergreen in there.

 

[theoldwizard1]

Pressure test it.

A couple of days before the pour, have the concrete company do a quick inspection to make sure they are happy with it.

Leave pressure in it when the concrete guys show up. Find the foreman and show him the gauge(s) and make sure he know that his company IS RESPONSIBLE for making sure the system will hold pressure after the concrete is poured and cured !