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Old 05-27-2009, 12:11 AM   #1
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new drains

I am installing a new bathroom in the basement.
I have had to jackhammer the whole area up due to elevation changes in the old concrete, so the whole area is exposed to the dirt right now. I have also exposed a section of the existing cast iron drain, about 6ft.
I will be breaking into this to go to the new area that will be picking up a sink, toilet and shower. (and maybe a floor drain)
The sink and toilet P traps are above ground, so they are easy. The shower and floor drain will have the P trap in the ground. Does the bottom of the P trap need to be above the elevation of the main cast iron drain?
If so I can't make this happen as the run from the shower to the cast iron drain is about 1/2" over 10ft.
What other options would be available?


rrekih is offline   Reply With Quote
Old 05-27-2009, 06:45 AM   #2
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Toilet does not need a trap, it is the trap. Keep in mind that whatever you put under the concrete may need servicing at some point. Entry points for augers are handyier than digging up concrete.


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Old 05-27-2009, 06:50 AM   #3
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I don't see where you mention anything about venting... Is there already a vent ?? If there isn't a vent that can be used you will have to add 1
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Old 05-27-2009, 08:51 AM   #4
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In my opinion you are creating a future disaster. "P" traps stop sewer gas from entering providing there is proper venting but will not stop sewage back flow if the is any blockage or restriction in the main line. If it were me I would install a sewage pump system and connect to the stack higher up. Sewage pump systems have back flow preventers.
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Old 05-27-2009, 10:07 AM   #5
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Where the bottom of the P-trap ends up is not an issue. You should have 1/8" per foot of fall on the pipe between the trap and where you connect to the drain. You could get away with as little as 1/16" or as much as 1/4" but 1/8" is best to move solid waste with the flow of water. Outside those parameters you will have problems with solid waste getting stuck in the drain and causing problems. A 10 foot run only requires 1 1/4" of fall. If you can not get the required fall consider raising the floor in the new bathroom enough to get the required fall.

I do not see the disaster "hayewe farm" is mentioning in the above post and if you can avoid a powered solution you should do so. Sure, a sewer can back up but you would have the same problem with the existing floor drains anyway. However "kenmac" brings up a good point about venting. Be sure you plan a vent for each fixture.

It might be a good idea to invest a couple of bucks in one of the plumbing books available at the big box stores. I find the Black & Decker or Sunset series pretty good DIY instruction if you can find them.

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Old 05-27-2009, 10:47 AM   #6
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I have attached a rough sketch of what I intend to do.
Yes I will adding a clean out and the old does have clean outs already. (not shown)
I would like to stay away from powered drains.
Attached Thumbnails
new drains-drain-vent.jpg  


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