Sdr 35 pipe depth and strength

[IAm_Not_Lost]

Figured I would post this in this area as it has more to do with outdoor pipes.

Any of you guys or gals specifically knowledgable about schedule 35 pvc septic pipe depth strength? I just had a propane truck run over my sdr35 line that goes from the septic tank itself to the area where the leach field is. The 4” pipe is buried at about 18”.

The ground is pretty well compacted in that area, but obviously it’s not somewhere we have traffic going over. This guy just didn’t see the rocks I have outlining the driveway and decided to make a straight shot to the propane tank.

Just has me nervous. Some sources online say 12” of minimum depth will support a huge amount of weight, other less formal sources say that sdr35 can never have traffic, which doesn’t seem correct.

 

[John Gayewski]

Your leach field should not have any traffic on it whatsoever. Not only for damaging the pipe, but the soil should be loose for leaching purposes.

Sdr 35 is pretty weak, but I'm not sure anyone makes that type of pipe (for a leach field) in sched. 40.

I'm sure someone probably makes it but it's not common and probably expensive.
No sdr35 can't take traffic.

 

[Sponsor]

 

[Tuttles Revenge]

This is the Side Sewer FAQ for Homeowners in Seattle.

There are two pipe products that are most commonly available. ▪ If you will have greater than 18” of cover over the pipe as measured from the crown of the pipe, PVC pipe – ASTM D 3034 SDR 35 is acceptable. ▪ If you will have less than 18” of cover over the pipe as measured from the crown of the pipe, PVC pipe schedule 40 – ASTM D 1785 with fittings per ASTM D 2466 and D 2467 is acceptable. PLEASE NOTE: This is a solid wall pipe, also referred to as “well casing”. Cellular core pipe is NOT acceptable.

 

[IAm_Not_Lost]

Your leach field should not have any traffic on it whatsoever. Not only for damaging the pipe, but the soil should be loose for leaching purposes.

Sdr 35 is pretty weak, but I'm not sure anyone makes that type of pipe (for a leach field) in sched. 40.

I'm sure someone probably makes it but it's not common and probably expensive.
No sdr35 can't take traffic.

Right, as I noted, they didn’t drive over the leach field itself where the pipe is perforated, just the solid schedule 35 pipe going to the leach field. Just a driver who didn’t pay attention.

Can you reference anything with regards to sdr35 not being able to handle any traffic? I see some people have the opinion you do, yet most pipe websites have the data for their sdr35 that note it can handle traffic of significant weight at a minimum of 12”. I was just looking to ensure that I was interpreting that correctly.

 

[John Gayewski]

Right, as I noted, they didn’t drive over the leach field itself where the pipe is perforated, just the solid schedule 35 pipe going to the leach field. Just a driver who didn’t pay attention.

Can you reference anything with regards to sdr35 not being able to handle any traffic? I see some people have the opinion you do, yet most pipe websites have the data for their sdr35 that note it can handle traffic of significant weight at a minimum of 12”. I was just looking to ensure that I was interpreting that correctly.

I can note the ovaled sdr35 I've encountered at depths deeper than that.

What does "can handle" mean? Meaning it doesn't shatter or oval or crush? If someone is claiming sdr35 can handle traffic they have probably never held it in their hand. A person can oval it with their hand. Since it's so thin it doesn't readily break. But bent pipe and ovaled pipe has failed. It doesn't really matter what a manufacturer actually means by the word "fail".

I guess I don't know the point of your wonder. You want to know if something broke, go lol at it. No one is gonna be able to tell it it's fine. It could be ovaled, crushed, or fine.

 

[IAm_Not_Lost]

I can note the ovaled sdr35 I've encountered at depths deeper than that.

What does "can handle" mean? Meaning it doesn't shatter or oval or crush? If someone is claiming sdr35 can handle traffic they have probably never held it in their hand. A person can oval it with their hand. Since it's so thin it doesn't readily break. But bent pipe and ovaled pipe has failed. It doesn't really matter what a manufacturer actually means by the word "fail".

I guess I don't know the point of your wonder. You want to know if something broke, go lol at it. No one is gonna be able to tell it it's fine. It could be ovaled, crushed, or fine.

The point of the “wonder” is if anyone has actual professional data on the rated burial depths.

For example, here is an excerpt from Westlake Pipe:

“The Unibell PVC Pipe Association Handbook of PVC Pipe, Section
7.8.3 states:
“A minimum cover height of 12 in. is recommended for PVC
(SDR35) pipe subjected to highway loads of up to 18 kip axle.
To prevent cracking of the road surface, special attention should
be given to the selection, placement, and compaction of backfill
material around shallow buried flexible pipe (such as PVC pipe) …”

That seemed a little shallow to me, so I was looking for any other professional guidance. Yes, I can just check on the pipe in both locations, but that will be about three hours of digging as the area is hard and compacted and frozen. So I was just looking to confirm that at 18” burial depth in well compacted soil that there is no reason that SDR35 would have an issue with that.

 

[John Gayewski]

Yes there is reason to worry about it. Sdr 35 should only be buried where necessary and never driven on. Simply becuse I've dug up sdr35 that has badly warped from being buried. Who knows why? Maybe when they backfilled the pipe they did a bad job, maybe the elevation of finished grade was lower at one point and there was heavy traffic over it, not really sure. But from experience it does happen.

You can find all of the data that says it's safe, but I'm telling you I've dug up pipe that was ruined. On more than 1 occasion in fact. Your can choose to accept that or not it doesn't effect me. It's just info for you.

Your may find that your pipe is fine. If I were you I would just sit tight and look for signs of failure rather than did it up.

 

[IAm_Not_Lost]

Yes there is reason to worry about it. Sdr 35 should only be buried where necessary and never driven on. Simply becuse I've dug up sdr35 that has badly warped from being buried. Who knows why? Maybe when they backfilled the pipe they did a bad job, maybe the elevation of finished grade was lower at one point and there was heavy traffic over it, not really sure. But from experience it does happen.

You can find all of the data that says it's safe, but I'm telling you I've dug up pipe that was ruined. On more than 1 occasion in fact. Your can choose to accept that or not it doesn't effect me. It's just info for you.

Your may find that your pipe is fine. If I were you I would just sit tight and look for signs of failure rather than did it up.

Appreciate the response. Thank you. Yes, should be easy to see soon enough if there is any failure.