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Any advice on how to get the correct pitch in an underground downspout run?

Any advice on how to get the correct pitch in an underground downspout run?

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  #1  
Old 08-27-18, 04:15 PM
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Any advice on how to get the correct pitch in an underground downspout run?

I tore up 35' of ADS (the triple wall white on the outside / black on the inside 4" piping) piping that is part of underground piping for running downspout water to the woods.

This stretch had standing water at the end . When digging it out / taking it apart, water was coming out the 'high' end .

It was put in 7 years ago? and I remember the guy mentioning how rocky the ground was... but that he was putting the rocks back under the pipe run.

Over time, I guess some rocks moved up and changed the pitch.

Any tips on how to get the right pitch on this run?

I bought new ADS pipes... I cut 'windows' in the top of the old ADS pipes. I envision putting in dirt, then laying the old pipes in there, run water in there and make sure it flows right.

Certainly not high tech. I'm just stumped how to really get a steady pitch along the run with pipes that could have a bit of a bend over the length, etc.

It should be 1/4" / foot slope? that's only 9" ver 35 feet. not much to notice?

thanks!
 
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Old 08-27-18, 04:51 PM
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I use a level. If my level is 4' long I tape something that's 1" thick on one end. If my level is 2' long I tape something 1/2" thick on the end. Then when working all you have to do is lay the level on the pipe and center the bubble. The spacer block on the end of the level builds in the proper slope.
 
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Old 08-27-18, 05:13 PM
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damn that sounds so simple : )

as you work, you are putting dirt under spots as needed to raise / scrape away dirt to lower. how do you make sure it's all compacted / settled before closing it all up? I was wetting the trench / making a mud soup to try to settle dirt I disturbed taking out rocks. Now I'll build things up get things right and wet things down to settle the dirt / compact it?
 
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Old 08-28-18, 07:33 AM
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I use a line level attached to a stretched string. Once you find level, then adjust string to correct pitch and use as a reference to get the correct pitch on the pipe.
 
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Old 08-28-18, 07:33 AM
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You can't compact mud or soup so you have to let it dry enough to compact. When digging I try to pay special attention so the trench is the proper depth and sloped as needed so the pipe can lay on virgin/undisturbed soil so there isn't a compaction issue. If you are putting the pipe on fill then I use a tamper to compact the fill underneath the pipe.
 
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Old 08-28-18, 09:15 AM
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Slope it right as you excavate... yeah, I wanted to dig out these big rocks (some about the size of a volleyball / small basketball?, some baseball size that were under the route. so it's disturbed : )

I tried the string idea when trying to find where the high spots were. But you want the string over the pipe path / it keeps getting in the way.

harbor freight has a 4 - 5' level for
 
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Old 08-28-18, 01:02 PM
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the 1/4" per foot is the min, if you get more that works even better.

Forget string, take any size level and attach to a 2x4x 8' use that as your guide to dig the tench,

Dig a little to much, just fill it in and step it down, nothing too complex. As long as you have good slope the minor flat spots will work out!
 
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Old 08-28-18, 03:48 PM
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iThanks!

tape a level to a 2x4.... I was thinking that but then saw at harbor freight a 5' level for $10. But having second thoughts now that someone else more knowledgeable validates my 'cheap' approach.

But more important, I may be near the minimum slope over 35' or so... I guess a level string then measure the distance down to the existing pipe i need to connect to lets me know if I've got 'sope to spare' or not.
 
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Old 08-28-18, 04:49 PM
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Originally Posted by babaganoosh
Any tips on how to get the right pitch on this run?
A The water is a hose is always level.
To level things over a long distance, I Just use a garden hose and duct tape some clear plastic tubing to the end. Soft 3/4" plastic tubing will sorta screw into the famale connector, seal with duct tape. The soft plastic stretchs over the male connector, seal with duct tape. Fill with water. The water level at each end will always be the same. Works over any distance, just connect more hoses.

B Reuse old gutters to get the slope right, then add the pipe.
I did something like this decades ago with my father. Buried one drain pipe that ran under a gravel driveway, and another that ran under the yard. We dug the trenches, scompacted the subsoil, put down some 2A stone (gravel with sand/dust) then worked out the slope using some old half-round gutters we had laying around. Set the PCV pipe directly on top of the old gutters, then backfilled. Figured the old gutters would help prevent sagging.
 
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Old 08-28-18, 05:04 PM
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Before back-filling, pour some water into the pipe to see that it flows as intended.
 
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Old 08-29-18, 05:16 AM
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Unless the dug up 35 foot section of pipe is at the end of the line, the slope of the replacement will be determined by the levels of the 2 existing connecting points. If at the end of the line, make the slope as steep as conditions and your back will allow. Good luck.
 
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Old 08-29-18, 10:21 PM
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For a 4 inch diameter by 10 foot long length of flexible drainage pipe insert a 12 foot long 2x4 in the pipe. This holds the pipe straight for the entire length while you can use the level on the top of the pipe. Place the pipe in the ditch and backfill all but the ends and then move on to the next section of pipe. You do need the room to remove the 2x4 after the pipe is securely buried in the ground.

Or you can use rigid piping. More fall is always better than too little.
 
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