Which is preferred copper or pex under the slab? In my 24x24 garage I will have in the back corner the rough in for water, drain and electric. So 24' under the slab, 28' across the driveway to house foundation and another 30' inside house to main connection. So I was looking at 100' of coiled copper, but should I use pex? Which size is best. Eventually there may be a full bathroom/kitchen on second floor.
copper or pex under the slab
- Thread starter Theruse
- Start date
doublearon98
Well-known member
Forget copper. Pex is the way. Use conduit to run through the ground and concrete, then you can push all your pex through. It's a great benefit incase you ever need to run new pex.
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samss
Well-known member
What he said. 
3/4" Pex in 1 1/2" conduit should suffice.
3/4" Pex in 1 1/2" conduit should suffice.dcg9381
Well-known member
Pex. Period.
3/4" size.
As others have said, sleeve the PEX (for best practice). Use electrical conduit with sweeps, etc. 1-1/4 or 1-1/2.
3/4" size.
As others have said, sleeve the PEX (for best practice). Use electrical conduit with sweeps, etc. 1-1/4 or 1-1/2.
rburke65
Well-known member
You want to do the PEX...NOT copper
I'll agree with the Pex and sleeving it as well.
Sounds like a plan. I was going to run 2 x 1 1/2" conduit for the main electrical and the second for low voltage and internet. So adding a 3rd line for water makes for one easy trip to the electric supplier. I also will be running a 3" PVC line for drain. Thinking of running it right up the middle of the right garage door which lines up well with the trench to the house. I will be installing a two post lift so the middle is best to avoid the deeper pad area reinforcement for the lift posts.
Beauregard
Well-known member
And make certain, when you're pouring the pad, that a worker doesn't step on the conduit.
I had this happen, which caused the conduit to break at a joint and then fill with concrete.
Didn't catch it until weeks later when we were fishing the lines.
I had this happen, which caused the conduit to break at a joint and then fill with concrete.
Didn't catch it until weeks later when we were fishing the lines.
dcg9381
Well-known member
I've found electrical PVC conduit to be pretty robust... The only catch is making sure it's secured and capped during the pour.
Kaizen
Well-known member
Damn I can’t see how anyone could break a schedule 80 duct. Maybe joint was not glued correct
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spudley
Well-known member
Scd 40 would be tough to break without trying hard.
OP...use wide sweep elbows in your conduit and in that 3" drain line.
OP...use wide sweep elbows in your conduit and in that 3" drain line.
I am assuming both sch40 and 80 are acceptable. In checking NEC no more than 4 qtr. bends (360 degree total) between pull points, so will have to do some careful alignment to feed tubes through center (with deeper 7" section for 2 post lift support) to end point in right rear corner. The only 90 degree I hope to use is from under the slab to the surface.
Before you buy parts, check you local plumbing code, You may need a 4" main drain under the slab.
I like running electric along side the building to come up with standoffs and go straight through the siding into the back of the panel.
Another thought. If you haven't looked recently, not only is PVC much more expensive than it was but it may be tough to find what you need. Get your stuff as soon as possible so you have it on site when needed. In addition to going to a electrical supply store, check out Supply House.com for your PVC fittings. They don't stock a ton of different electrical fittings but what they have will be quite a bit less expensive than Lowes/HD. Lowes/HD will sell the pipe cheaper than about anyone BUT they hit you pretty good on any fittings.
https://www.supplyhouse.com/Electrical-PVC-Fittings-32770000
Their free shipping threshold is down to $99.00, which won't be hard to hit.
https://www.supplyhouse.com/Electrical-PVC-Fittings-32770000
Their free shipping threshold is down to $99.00, which won't be hard to hit.
Check the code to see if schedule 80 required to be used under the driveway for the electrical run?
spudley
Well-known member
For electric applications Scd 40 is OK underground. Any exposed conduit should be Scd 80.
For water, I don't think it matters.
FWIW, I ran AL MHF 2-2-2-4 through 1 1/2" conduit with an LB on the house and an LB on the detached garage, and used two wide sweep 90's. It went through OK but 2" conduit would've been easier. MHF can be direct buried @24" or 18" in conduit.
Innovate1
Well-known member
You should check your local requirements. I used 1" CTS polyethylene with compression fittings at the ends and ran that through 2" PVC. Required separation between water line and sewer is 10' here but they allowed sleeving the water line if the sleeving extended to where the separation was 10'. The local inspector suggested sleeving it with long sweep bends up through the slab and mentioned that would allow replacement if ever needed. I used 24" radius conduit bends and for the 40' straight run used 20' sections of PVC water pipe with gasket seals. I just looked up the poly tubing at Menards where I got it and saw it isn't sold in a long list of states so I am guessing it isn't allowed many places. I think some places still require metal water lines.
As others have mentioned your drain line may need to be 4", mine was. And if I recall correctly the 4" had to continue to the vent. On my house done about 20 years ago the vent through the roof was reduced to 2" but that isn't allowed anymore, at least here.
I ran 1-1-2-4 of AL XHHW through 1-1/2" conduit with a long sweep at each end and had no trouble. I did set up some pulleys on the pull rope to give me a better angled and had someone to guide the wire in at the other end but it went through easy. MHF should be just a bit harder with the twists but I think you should be fine, especially with only one bend. I had some trouble getting long sweep bends in other than 2" conduit but had limited space in some areas so needed to stick to 1-1/2" conduit. So I bent my own with steam to heat up the pipe.
As others have mentioned your drain line may need to be 4", mine was. And if I recall correctly the 4" had to continue to the vent. On my house done about 20 years ago the vent through the roof was reduced to 2" but that isn't allowed anymore, at least here.
I ran 1-1-2-4 of AL XHHW through 1-1/2" conduit with a long sweep at each end and had no trouble. I did set up some pulleys on the pull rope to give me a better angled and had someone to guide the wire in at the other end but it went through easy. MHF should be just a bit harder with the twists but I think you should be fine, especially with only one bend. I had some trouble getting long sweep bends in other than 2" conduit but had limited space in some areas so needed to stick to 1-1/2" conduit. So I bent my own with steam to heat up the pipe.
Always use 1" poly (black) water line in a proper trench (the stuff for wells) .... I guess you could trench under the slab. I always run it around and into the building where I want it. On the house side --- use what is in the house to the point of entry for the 1".
Have never seen standard PEX used as a feed outside to any building
Have never seen standard PEX used as a feed outside to any building
rlwhitetr3b
Well-known member
What they said above.
Related story...
When I was in electronics tech class a instructor use the story of a builder that used acid core solder on the copper pipes in bedded in a slab. After some time the acid dissolved the copper and all of it had to be replaced.
Related story...
When I was in electronics tech class a instructor use the story of a builder that used acid core solder on the copper pipes in bedded in a slab. After some time the acid dissolved the copper and all of it had to be replaced.
Los_Control
Well-known member
You have to understand you watching the wrong train.
Pex is used for Gas lines ... new underground water lines.
I am replacing my water supply lines under the house .... going pex ... Nothing else will perform the same.
Pex will freeze, expand, then thaw with no damage .... stick that in your hat.
Just saying.
Amazing the price increase on items. Just a few weeks ago when I was preparing my cost estimate I took photos of items at HD and Lowe's. Not only lumber but other items like PVC, electric boxes, etc. Minimum of 10% and as much as 25%. increase since then. So I am ordering items such as trusses, siding, etc. way ahead of need. "Just in time inventory" is a thing of the past. I agree on HD and Lowes charging reasonable price for conduit, but charging outrageously for the fitting (razor blade model). So will check out Supply House. Surprised that drain and water have to be 10' apart in some parts of country. That means two trenches. Crazy. Our code says drain and water can be in same 24" trench at 30" depth. One thing not clear about- does drain and water have to be 30" below grade when exiting slab to beginning of trench or do I have to be 30" below grade under slab at beginning.
1320stang
Well-known member
Use PEX-A.
jrsavoie
Well-known member
Is there inner duct big enough to pull a water line through?
Innovate1
Well-known member
The depth requirement is for freeze protection. In some areas where temps are only about 20F minimum lines are sometimes run at 12" down. Under the building the freeze depth is considerably less even if the building is unheated. Drains don't have to be as deep as water lines. Again, you need to check what the local AHJ requires but usually the depth requirement is exterior and the line has to exit the slab edge or foundation at the locally required depth. Inside there is often no minimum if under a slab. If it is at 30" at the edge of the building you can slope up from there inside.