Sand layer for PVC irrigation pipe necessary?

[bcarwell]

I'm in Central Texas laying 1500 feet of SCH 40 1 1/2 inch irrigation pipe in an 18 inch deep trench. Soil is rocky, limestoney, colleechy.

First, is it really necessary to add a sand layer ? I'm told it is, to protect the pipe from the abrasion of the rocky soil when it shifts.

Assuming it is, how thick should it be- 6 inches ?

And do you add the sand and then the pipe, or can you just dump the sand over the pipe after you've put the pipe in ? If you add the sand first, do you then cover the pipe with more sand after you've put it in the trench before backfilling with the rocky soil ?

I don't expect this to last 20 years and don't want to overkill (especially since adding sand in 1500 feet of trench is a hassle) but on the other hand don't want to be re-doing the job in five years.

Thanks for any help.

Bob

 

[ustmd]

Hiya Bob,

I am out east of Austin in heavy clay.

We bedded all of our PVC water pipes/septic pipes (~1200 ft in total) in ~12" of sand. Supposedly it was to protect the pipe from soil expansion.

I don;t know it it made a difference. In 10 years, I have had two leaks--one from a defect in an elbow and one from a separation at a joint.

The nice thing about the sand, however, is if you are digging in or near the pipes and start getting sand, you know you are close.

Sorry, I couldn;t be more help.

 

[F250DSLPWR]

Our ranch is out at Oatmeal, Tx. NW of Austin in rocky limestone soil. Over the years we have put in lots of septic systems in and around the central Tx area. I would highly suggest cleaning out the trench, putting in a layer of sand in the bottom. placing the pipe, then cover over with sand around the sides and top. When glueing up your PVC. Use both primer and cement, push the the couplings all the way together and then twist, make sure they don't pull apart. If this is a large water line pipe with gaskets, make sure you have concrete backstops to keep the pipe from pushing apart. Hope this helps.

 

[AchingBack]

Yes, by all means, bed schedule 40 in sand. I've seen too many jobsites where the sch. 40 was back filled with sharp shale. It isn't any fun to dig up and repair leaks; because as soon as you fix one, another pops up. Sand, granite, topsoil; all will work.

Now that I've said that, as a professional landscape contractor, under most circumstances, I used class 200 PVC coming out of the valves. I don't see how you need to spend so much money on Sch. 40. Check with the local professionals.

 

[EddieWalker]

When I worked in CA, it was required to use sand on all the pipes. First the sand went into the trench and was smoothed out. Then the pipe was installed and inspected in place. Then the sand was dumped on top of the pipe and jetted with water. The water settles the pipe and makes it form around the pipe and gets rid of air pockets in the sand. With enough water, the sand will settle and self compact around the pipe. The water is very important if you want to drive over that ditch or build anything over it. If not, who knows how much movement or settling you will get over time?

When running pipe over distance, gasketed pipe is the best way to do this. The gaskets allow the pipe to move in and out and not break with the movement of the soil. The sand will stop a lot of this, but with distance and some soils, you can still have pipes pull apart from time to time.

Good luck,
Eddie