Basic ABS underground Plumbing

When I was beginning to work in the trades, I was told the most important things to know about plumbing are:

• Payday is Friday
• It all goes downhill
• Don’t eat the mints or peanuts at the counter

After years working in the construction, I became a responsible person for the company which employed me and then a general contractor and responsible to oversee the project.

The photo above is of the ADU (additional dwelling unit) project I am building in Riverside CA.

• On the right side of the photo outside the forms you see a 4” ABS pipe coming from the trench. That is a clean out. I placed them within 50’ of one another and near ever 90” bend.
• In the front of the photo is a 10’ tall 2” ABS pipe. It is how I pressure tested my system and proved it for the inspector. If you allow your eyes to follow the trench line you can see where to slightly offset pipes of the ABS join. One is a 2” and the other is a 4”. The 2” is the 10’ stack used to run the pressure test and is the kitchen sinks drain. The other is another clean-out at the end of the main drainage system. It is 4” ABS. I use double clean-outs so I can snake both directions if need be.
• The offset was created by two 90 degrees fittings. I used Combination fittings here with a slow or long sweeps. The combo can be installed vertically or horizontally. Each change of direction causes an increase to the restriction in the flow of the line. The are charts which tell you how to calculate these restrictions and those for the reason you’re running the drain line (sink, tub, shower, laundry, toilet ect…,)  
• Each vertical pipe along the forming wall is connected to the 4” main trunk line by a

4’ X 2” slow sweeping combination T. The vertical stacks which rise above the form were attached using San-tee. They are cheaper than the comb’s but they don’t take as long to make the 90 degrees turn and they are only to be installed vertically. These turn slower than the sharp 90 degrees turns that aren’t for underground in CA.

A few tips on installing the plumbing. If you create something in the shape of a S in you line of plumbing or its offshoot. That will create a siphon. The S stands for Siphons do not pass inspections.

It however is true that plumbing runs downhill. You need to check your local codes to determine the slope of the run. This ran at ¼” per foot. Some people have thought that I’ll run mine real steep and it will fly through. This doesn’t work because the water will fly around the waste and not push it down through the system. An occasional fall is fine. Sometime you need to run a line vertical. Short runs are fine but not longer than 5’ in this city.

The other thing when you are digging your trenched you need to dig them with the proper slope or you’ll be compacting them with the proper slope to ensure the pipe doesn’t sag once the back fill has been completed.

The boxes are for the tun lines. They allow me to have room to adjust the traps and overflows for the shower tub combinations. The 4” ABS stacks seen are for the toilets and will be cut flush to the tiling one installed. This allows the toilet flange to be installed flush with the flooring.

 The half of the 2” trap hangs there to remind me and tell the inspector that the laundry room’s drain needs a trap and a stack of to the side.

Use the proper glue and don’t be stingy. Get the bigger cans and apply it to both items to be joined. Once they fitted give then a quarter turn to help smooth out the internal glue in the joint.

Usually, the drains under slab is placed between 1 and 3 feet, but it needs to be able to get the proper slope. These footing are 12” by 24” deep they are in caleche soil which is a type of clay soil that shafts when wet, and hard as rock when dry. The drain line can cross through your footing but you cannot save digging by running them in your footings.

Take your time to draw out what your doing it will help you when picking up the materials.

Note: Images on this blog site are from a free source or taken by the author. No image or group of photos is intended to represent the people the author serves. The author does not care about Race (that is a politically correct term that he does not like because we are all of the same Race, the Human Race. He prefers the term ethnicity, color, religion, sex, gender, marital status, disability, genetic information, national origin, source of income, Veteran or military status, ancestry, citizenship, primary language or immigration status.) He is a service provider for all people. We will all rise together when we band together and help one another. Joseph Erwin is a Real Estate Broker, DRE # O2131799, and a CA general contractor # B 696662. He’s a member of the CRMLS and The East Valley Association of Realtors located in the Inland Empire region of Southern California. This writing is not to be used as legal counsel the author is not a lawyer and does not give legal advice other than consult a lawyer before acting.