# Separation of water and sewer



## Joe Engel (Dec 7, 2018)

Running discussion with plumber, 
2012 IPC, 603.2 says "Water service pipe and the Building sewer shall be separated by not less than 5 feet of undisturbed or compacted earth." 

But 603.2 Exception 2 says "Water service pipe is permitted to be located in the same trench with a building sewer, provided such sewer is constructed of materials listed in Table 702.2."

Table 702.2 UNDERGROUND BUILDING DRAINAGE AND VENT PIPE gives reference to all materials allowed  to be used within the building footprint or building drain system. 

In my experience, we always separated the two outside the slab either by 5 foot or on a shelf  in the same trench, 18" above the building sewer. Here is the deal... If a building drain meets code and you use the same material as in the slab outside the slab, then you should be able to run the water service in the same trench (his argument)... Opinions?


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## HForester (Dec 7, 2018)

Correct. Don't we commonly lay building drain piping and water distribution piping in the same trench under a slab on grade foundation? If it is not in the same trench under a slab on grade foundation, we certainly don't pay much attention to separation between the two.


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## jeffc (Dec 7, 2018)

The 2015 Uniform Plumbing Code, Section 720, requires a separation only if the sewer pipe is not approved for use inside of a building. Not the IPC but close.


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## Master Pipe (Dec 13, 2018)

You can take different decision after situation.


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## Joe Engel (Dec 21, 2018)

I assume the concern is cross contamination and the commentary might read that using the same grade of pipe as inside the slab, the need to replace the sewer pipe, if properly installed, is rare... old ways are just hard to let go


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## north star (Dec 21, 2018)

*# ~ #*

Joe,

IMO, ...the problem is not so much the installation of
both plbg. systems in to one trench, rather, when
there is a need to repair one or the other......The
potential to damage \ interrupt service to both systems
now becomes greater.......Repairing one system or the
other in its own trench is a lot neater & less problematic.

*# ~ #*


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## iOne (Sep 7, 2022)

Here's a more complete code citation (here from the California Plumbing Code CPC:



> 720.1 General
> 
> Building sewers or drainage piping of clay or materials that are not approved for use within a building shall not be run or laid in the same trench as the water pipes unless the following requirements are met:
> 
> ...



In other words, unless you're using clay or something weird, the water pipe and sewer can be in the same trench with no shelf.
Of course as noted above that makes it harder to service one or the other, but chances are if you're taking one out the other will need it also.


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## Joe.B (Sep 7, 2022)

We have been seeing a lot more of the "SDS" pipe. I know that's not the right term, but that's what everybody here calls it. It's PVC pipe with a compression fitting on one end, no gluing. It's a lot easier and faster to install, but it's not allowed in the building and if they use it outside we have to ask them to move the water line. They typically grumble and replace the SDS with PVC or ABS and glue. The reasoning behind this requirement makes sense to me. And if both the IPC and UPC agree that tells you something right there.


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## steveray (Sep 7, 2022)

SDR 35...typically green here


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## ICE (Sep 7, 2022)

Joe.B said:


> It's PVC pipe with a compression fitting on one end, no gluing.


I can’t say for sure but that seems like a weak defense against roots.


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## Gregg Harris (Sep 30, 2022)

Where water service piping is located in the same trench with the building sewer, such sewer shall be constructed of materials listed in Table P3002.1(2). Where the building sewer piping is not constructed of materials indicated in Table P3002.1(2), the water service pipe and the building sewer shall be horizontally separated by not less* than 5 feet (1524 mm)* of undisturbed or compacted earth


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## ICE (Sep 30, 2022)

Gregg Harris said:


> Where water service piping is located in the same trench with the building sewer, such sewer shall be constructed of materials listed in Table P3002.1(2). Where the building sewer piping is not constructed of materials indicated in Table P3002.1(2), the water service pipe and the building sewer shall be horizontally separated by not less* than 5 feet (1524 mm)* of undisturbed or compacted earth.



Five feet seems excessive.


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## e hilton (Oct 1, 2022)

ICE said:


> Five feet seems excessive.


Thats for unlisted pipe materials.


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## ICE (Oct 1, 2022)

Table P3002.1(2). is a Residential Code item and California did not adopt the plumbing portion of the residential code.   I am surprised that a five foot separation is mentioned in a code but here it is.  

*P2905.4.2 Water Service Installation*
Trenching, pipe installation and backfilling shall be in accordance with Section P2604. Water-service pipe is permitted to be located in the same trench with a _building sewer_ provided such sewer is constructed of materials listed for underground use within a building in Section P3002.1. If the _building sewer_ is not constructed of materials listed in Section P3002.1, the water-service pipe shall be separated from the _building sewer _*by not less than 5 feet, measured horizontally*, of undisturbed or compacted earth_ or placed on a solid ledge not less than 12 inches above and to one side of the highest point in the sewer line.  _

California Plumbing Code has this:
720.1 General. Building sewers or drainage piping of clay or materials that are not approved for use within a building shall not be run or laid in the same trench as the water pipes unless the following requirements are met:

1. The bottom of the water pipe, at points, shall be not less than 12 inches above the top of the sewer or drain line.

2. The water pipe shall be placed on a solid shelf excavated at one side of the common trench with a clear horizontal distance of not less than 12 inches from the sewer or drain line.

3. Water pipes crossing sewer or drainage piping constructed of clay or materials that are not approved for use within a building shall be laid not less than 12 inches (305 mm) above the sewer or drain pipe.

For the purpose of this section, “within a building” shall mean within the fixed limits of the building foundation.


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## steveray (Oct 13, 2022)

Do you have to measure it horizontally or can you go with the curvature of the earth? Or is that what the "horizon" is....?


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