PVC expansion Exterior

[kwired]

is expected to be more than 1/4 in." It doesn't say "length change from the time of installation." So it can be the length change between any two points in time, i.e the hottest day and the coldest day.

Well said. that is how I have always understood it.

The thing about an elbow is that a PVC strap is designed to allow the PVC to move axially (along the long dimension) but not tranversely (side to side). And any change in length of the pipe on one side of the elbow would require a traverse motion of the pipe at the first strap on the other side of the elbow. So it will induce bending in the pipe between the elbow and that first strap.

Every installation has it's conditions. If the expected length change is pretty minimal and you don't have the first strap on other side of the elbow too close it may be fine.

For smaller conduit sizes maximum distance between supports is 3 feet, for larger sizes that can be 5 feet - gives you more free conduit if your last support before the elbow is pretty close and your first strap after the elbow could be maybe four feet from the deflection point.

 

[Eddie702]

If you have long expansion fitting and only 1" of calculated change in length, you have some room to play with and wouldn't necessarily have to install at mid range of the fitting.

If you have more potential length change than the length of the fitting, you are going to need more than one expansion fitting in the run. But you sort of need to secure the mid sections or over time things could move far enough that one of those fittings eventually pulls apart.

I was just using a random example