# Help with digging depth



## GaudetteConst (Jan 11, 2018)

Hi, I am planning my first garage under with basement adu. I was wanting an opinion of my dig depth to male sure it still has flow to the city sewer. The sewer depth is 90in. The length from the house to the sewer is 1512in. The lot is 12in less elevation from the manhole grade. So I need for fall 31.5in. min. That would put me at 58.5 dig depth from the manhole but with 12in elevation change I subtracted the 12in to get a dig depth of 46.5 in. Does this sound correct? I don't want to get this done and not have the correct flow.


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## DATEC (Nov 4, 2017)

When in doubt, Hire it out. If you are not sure and this is your first leave it to the pros and work with them (for free, if they let you) and see what they do and how they do it. Other wise you could have a mess on your hands.

Sorry that's my best advice I can give ya.


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## Morning Wood (Jan 12, 2008)

Seems ok. You using 1/4”/ft I take it. Is that 4”? That’s a long run. You’ll want some clean outs.


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## dayexco (Mar 4, 2006)

is there a service wye/stub in place already? if so, what depth? 

if no service wye/stub in place, you know you can't go by the invert elevation of the main at the manhole...you need to shoot the inverts of the manholes on the uphill, and downside of your proposed connection, calculate what grade the main was laid on based on those two elevations, taking into consideration the distance from both. if it's like our local sewer dept..our flowline of our service has to be at least half the diameter off the invert of the main line.

does your sewer authority tap your mains for you if one not in place? or is it left up to you? if it's an old clay/concrete/AC line...i would rather doubt you'll have the proper equipment to make that connection.

now the fun stuff. do you have a lot of experience operating equipment? you have experience digging around existing utilities? fiber optic/ cable coax/ nat. gas lines/ power lines?

if you haven't had much experience in operating, and if the mains(water and sewer) you're exposing are AC/clay/CI...and you "bump" them wrong, you'll have a ditch full of water or sheet, and good chance of filling surrounding homes basements full of water or sheet.

good luck.


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## GaudetteConst (Jan 11, 2018)

Thanks. This is helpful information. It is a 4in line. We don't have a stub and we have to do the tap ourselves, which is common here when there isn't stub. It should be CIPP, I am checking tomorrow. Also no utilities in the way luckily. We have an experienced operator just not much knowledge in this area and if it seems too much for him I do have another excavator in mind as a backup plan. Very good points with the calculations. I'll give the water bureau a call in the morning to get more input on what you mentioned with the connection and depth. Also I got ahold of an excavator that I knew growing up that has since retired and is coming out to look at it. Thank you this has given me a good idea on the questions to ask. I have done other projects similiar but usually the sewer run is 30ft max and so slope wasn't an issue.


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## B.Johnson (Sep 17, 2016)

Slope is always an issue.


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## dayexco (Mar 4, 2006)

B.Johnson said:


> Slope is always an issue.


The old saying. 

Only two things ditch diggers need to know. 

Sheet flows downhill

Payday is Friday

Sent from my SCH-I545 using Tapatalk


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## dayexco (Mar 4, 2006)

see if your supply house has these, i love em

https://www.insertatee.com/product-applications/tapping-sewer-pipe


on edit, should you use this product, make SURE your hole saw is the diameter insert a tee specifies...or it won't seal properly. don't ask me how i know this

where in oregon are you?


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## GaudetteConst (Jan 11, 2018)

I am in portland.


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## dayexco (Mar 4, 2006)

GaudetteConst said:


> I am in portland.


my daughter lives in klamath, my granddaughter, her daughter was involved in a toboggan accident near crater lake on new years day, and was airlifted to portland to a pediatric hospital. she's home now, and doing great

my wife is in oregon now, i must say...the treatment my granddaughter/daughter/wife have received there...were it not for all the freakin mountains, i might have moved there.

there are MANY kind people in klamath and portland.


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## GaudetteConst (Jan 11, 2018)

I live towards mt hood and yes many people here are good people. I just found out that my buddy has a friend that has a transit and will shoot it for us. This will take away the guessing.


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## jhark123 (Aug 26, 2008)

Your sewer dept might be able to recommend a guy to do the tap.


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## Fouthgeneration (Jan 7, 2014)

I'd strongly recommend using 4" schedule 40 or better pipe, Stiffer, lays straighter, stronger, and better self venting then 3"... fewer service calls. less then 100.00 $ more for decades of trouble free service.......:thumbsup:

Long radius bends.... and clean out wyes. Place Kerb to house clean out OUT SIDE the house, why have the mess indoors????

I see no need for a 2% grade, especially with 4" piping, Boom, your floor can go down 16"....there are pages of posts discussing this.:whistling

You need to lay the pipe on hand dug UNDISTURBED clay or use rock fill and tamp lightly to prevent sags/ traps, no bombing the pipe string in on machine dug loose spoil....:sad:

At 125' you might need to allow for thermal expansion if all plastic pipe.


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