how much sand to put under sewer line?

[coachgeo]

Just about finished putting in 4" pipe with 1/8 slope for sewer for detached craft building with a small bathroom. Run is about 140'. trench is about 8" in the widest places and majority closer to 5". Only need 5" or less sand below pipe to make it sit on firm surface at right slope before burying it on top with soil removed to dig trench.

Anyone got a hint on how to calculate how much sand I need to do this?

 

[RCW]

Coach - you want to figure cubic yards. Is a 6" (0.5') average for trench width logical? How about 6" (0.5') under? (I would do that if frost heaving is a concern)

140' long x 0.5' wide x 0.5' deep = 35 cu. ft.

35 cu. ft. /27 cu. ft. per yard = 1.3 yards

 

[coachgeo]

....35 cu. ft. /27 cu. ft. per yard = 1.3 yards

1.3yards or 1.3 Q cu. yds.?

looking at lowes website - cheapest sand bags at .5 cu ft per bag comes out to, 70 bags at an approx total of 210$ Yikessssssss

 

[Eray]

1.3yards or 1.3 Q cu. yds.?

looking at lowes website - cheapest sand bags at .5 cu ft per bag comes out to, 70 bags at an approx total of 210$ Yikessssssss

Many local builders supply stores sell it loose by the ton and deliver it on a small truck with a dump. Much cheaper that way. You could probably have them drop a bucket full in the back of your pickup.

 

[85Hokie]

1.3yards or 1.3 Q cu. yds.?

looking at lowes website - cheapest sand bags at .5 cu ft per bag comes out to, 70 bags at an approx total of 210$ Yikessssssss

Geo,

that would be cubic yards....... cubic is derived from 3 numbers , yet again, most people when they talk about concrete, gravel, sand etc, the talk about it being in yarrrds.....most leave off the cubic because that is understood.

ONE cubic yard is 3' x 3' x 3'. IF you were to take a full size pickup truck and fill the bed struck full, you would have 8'x4'x2' more or less, 2.3 cu yds.

Rather than buy bags, go to the nearest mulch place, I am sure they will have sand, gonna guess about 40 bucks a ton.....just a guess, NOW we gotta convert sand yards to tons!!! 2300 lbs to 1 cubic yard, more/less , depending if wet or dry!

I would have them dump a scoop in truck , haul , lay down and then get more if need be...............just my 2 little pennies

 

[RCW]

Sorry about the lagging "cubic"

Do as Hokie said - there should be someplace around to get it bulk.

Sand is not the only option, pea stone, crushed #1 (small) would work also. Want something clean from dirt to prevent heaving in winter, and avoid large stone against the pipe and damaging it when backfilled.

Speaking of backfill - remember you want a decent cover also. Stray stone in your backfill can damage the pipe.

Good luck!

 

[RCW]

Correction - don't do EXACTLY as Hokie said - - -

DO NOT fill your pick 'em up truck to the brim! Might be a little more than it can handle!!

Good luck - much more economical options available, I'm sure.

 

[North Idaho Wolfman]

Did you put a tank on it?
If you didn't and if your feeding it directly from a toilet it will fail in a very short period of time, nothing to break down the paper and poo.
I've used a couple of 55 gallon drums to do the job, works like a charm.
Also get some starter for the tank as it need some bacteria to get going.

For the leach field I would do pea gravel over sand, as sand will fill in with debris too early and again fail.

 

[Tooljunkie]

He said poo....
Also check recycling depots too, up here crushed glass is free. Comes in a large tote bag and loaded with a forklift.

 

[coachgeo]

Did you put a tank on it?
If you didn't and if your feeding it directly from a toilet it will fail in a very short period of time, nothing to break down the paper and poo.
I've used a couple of 55 gallon drums to do the job, works like a charm.
Also get some starter for the tank as it need some bacteria to get going.

For the leach field I would do pea gravel over sand, as sand will fill in with debris too early and again fail.

No (additional) tank....... the drain is solid pipe not leach pipe. It going to the existing house septic tank.

Geo.....I would have them dump a scoop in truck , haul , lay down and then get more if need be...............just my 2 little pennies

As to trucking in some...... I don't own a truck. Tis why I looked at bags.

 

[cerlawson]

I'm a civil engineer. The main reason for bedding under a pipe is for uniform alingment AND TO PREVENT BREAKAGE due to the load of earth from above. If you have the typical PVC pipe and trench is not wide and unusually deep, I'd smooth up the "bed" for the pipe with earth from the trench tamped and backfill the trench with what came out. That typical pipe can stand a lot of abuse.

 

[coachgeo]

I'm a civil engineer. The main reason for bedding under a pipe is for uniform alingment AND TO PREVENT BREAKAGE due to the load of earth from above. If you have the typical PVC pipe and trench is not wide and unusually deep, I'd smooth up the "bed" for the pipe with earth from the trench tamped and backfill the trench with what came out. That typical pipe can stand a lot of abuse.

Yes I had heard it was mostly to protect pipe from breakage. My thought was though it would be easier to fill around pre installed pipe.

Go figure I did it wrong. See now I should have done bed first and measured slope on the bed and not the pipe.. but too late now. Pipe is in and glued. Much of the pipe is barely below surface of yard. Part of it is NOT below surface at all and I'll have to add dirt to cover it in a hump. Assumed shovels full of sand would be way to fill in below pipe once pipe laid to form needed bed. What came out with trencher is a clumpy hard clay thus assume this is not going to fill in well under pipe. Thought I would leave trench open a while with sand in it to let rain pack it in some before putting clay on top. Beside I got to run a Phone Cable in same trench. Letting it rain to pack down also works with my odd work hours makes it near impossible to do anything but 4 hours or less of work each time including set up and clean up. Took weeks to get pipe all in due to schedule and weather as it is.

Side note: Going to put no rot decking across trench that goes across driveway since it is least shallow trench area. Thought was to overlap approx 6" trench width by a foot on each side with deck lumber so weight of car passing over is spread more as it crosses the filled trench.

 

[RCW]

Coach - all is not lost.

I am NOT a Civil Engineer, but I did stay at a Holiday Inn Express last night.

Lawson is right.

Your trench really should follow the slope you intend to run the slope for the pipe. However, in upstate New York, you're usually digging out shale stone, etc., and trench bottoms will vary some. We don't often deal with nice gravel soil. We have to make that up with pipe bedding. Heavy frost in clay soils will pop distribution boxes all over the place - so here keeping water away from stuff is important.

How much does your trench bottom vary from your required pipe slope?

Is your soil real stoney/boney? Sandy, gravelly, or clay/hardpan?

What kind of PVC are you using? Schedule 40?

You could cut it at the bathroom end and pull it all out of the trench. Then re-level the bottom, put it back in and re-connect with a coupler.

If the trench is relatively constant - do as you planned. But, you better be damn sure you get a solid bottom under that pipe so it doesn't have low spots in it.

The driveway crossing would concern me (here anyway) for freezing, especially if only used intermittently.

What the hell was I thinking.....do you have any pictures??

 

[85Hokie]

Correction - don't do EXACTLY as Hokie said - - -

DO NOT fill your pick 'em up truck to the brim! Might be a little more than it can handle!!

Good luck - much more economical options available, I'm sure.

that was a theoretical filling of the truck - used for reference of size and shape
.....

thus the last line :

I would have them dump a scoop in truck , haul , lay down and then get more if need be.

I have filled many a truck full of ......."stuff" - and learned my lesson of dayum this stuff is heavy!

 

[cerlawson]

No problem with adding sand later to fill in around the underside, but be careful not to tamp it so much that you raise the pipe. As to using sand near the final ground surface remember it erodes easily.

 

[OldeEnglish]

Unless your ground is very boney with larger than 3/4" stone, you don't need sand. It's a good practice to cover with sand, but in all reality, clean fill works just fine. When the fill is a bit boney, just a thin barrier of sand is really needed. If your going to run a compactor over the trench if it crosses a driveway, cover with a good 6" of sand over the pipe to cushion the pipe from the compacted gravel. If it's running through the yard, the cover doesn't need to be compacted.

I prefer to lay underground on solid, compacted ground, and use something compact able to bring the pipe up if needed. Sand won't compact with a jumping jack or a plate compactor, it tends to spread out because it doesn't have any gravel in it as a binder. A quick pass with a plate compactor will help it settle. The old school way of spraying it with water (careful not to drown the ditch and float the pipe) works well to settle the sand and naturally compact it. We always covered the pipe by hand/shovel to prevent any large rocks dropping directly on the pipe.

I've laid underground many times in straight 3/4" or less crushed stone due to ground water. Never lay pipe in mud, the mud will eventually dry out and shrink. I never met an inspector that had a problem with it and can't recall ever having any broken pipe issues from it. Usually that happens when someone drives over a pipe sticking out of the ground with a piece of equipment .

 

[coachgeo]

my driveway trench is nothing but gravel and rock. looks like Im going to have to work more in this area to dig it out deep enough to cushion it all with sand and then put something else beside what was taken out while trenching over the top. That is all rock and gravel too.

Thank ya'll for all the input.

 

[lakebota]

don't buy clean sand, buy bedding sand that includes fines.


area of a 4" pipe is about 12.5 sq in, or say 12/144 = .0833 sq ft. (discounting thickness of wall, but good for calculating)
area of 6" wide ditch with lets say 12" sand depth = .5 sq ft

subtract pipe area from sand area .5 - .0833 = .4167 sq ft
amount of sand required is area x the length or .4167 x 140 = 58.3 cu ft of sand
convert to yards 58.3 / 27 = 2.16 cu yd I'd get 2.5 cu yd to be safe, even a more (4 to 5 (sand is cheap) or so to properly cover the pipe) and some trench marking wire or tape to put on top of the sand (that should cover the pipe at least 3 to 4 inches or more).

 

[RCW]

that was a theoretical filling of the truck - used for reference of size and shape
.....

thus the last line :

I would have them dump a scoop in truck , haul , lay down and then get more if need be.

I have filled many a truck full of ......."stuff" - and learned my lesson of dayum this stuff is heavy!

Trust me, just poking some fun!

I'm with you - I've done it a bunch of times, too!! Head toward home thinking "OH BOY - DON'T DO THAT AGAIN!"

 

[D2Cat]

We have a nearby mfg. plant that build pressure vessels. They sand blast so much they have a sand pile they load out with their loader, or you can shove as much as you want, no charge.

Maybe you have something similar nearby?