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Plumbing in the Home/Drainpipe for washing machine and concrete



I am doing a complete kitchen laundry room remodel.   The only way to put a drain pipe for the washing machine is to break open the wall placing the drainpipe inside the wall going down and breaking the concrete slab floor continuing the pipe inside the concrete floor to the other side of the wall to tie it in to a existing drainpipe.  Is this ok to put a drain pipe for a washing machine this way. The clean out will be in the house under the washing machine in the floor foundation.
Thank you

ANSWER: Hello Kay,
Is a qualified plumber going to be doing this work? I don't know what the physical situation is so it's difficult to determine if this is an acceptable installation. One big question comes to mind; is this new washing machine drain line going to be properly vented?

Every drain must include a P trap and be properly vented above the roof line. I saw no mention of a vent in your description. Without a trap or a proper vent, toxic sewer gases could enter the living area of this home.  

In California, the 2012 IRC codes are what is followed. Some local jurisdictions also have amendments/modifications but essentially follow that code.

Having a house on a concrete slab as both positive and negative consequences. Modifying or adding drainage piping with a concrete slab can be difficult and expensive. Make sure you use a QUALIFIED and licensed plumber for this work. There can be serious consequences if done incorrectly and you have to tear it all out and do it over.
Good luck, Dana

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Their use to be a washing machine on the opposite side of where the new washing machine is moving too.  The contractor will have the license plumber doing the work. Can the plumber use the existing vent on the opposite wall? or does a new vent need to be added?
(remember from above he is tying in the new drain to the old one.)
Alternative idea was to put the gas dryer their :The contractor does not want to do because he said of cosmetic reasons.  Was to put a gas dryer on that side and moving the gas lines and vent to the side wall.  (their is a brick fireplace on the other side of the wall that the washing machine or the dryer would go.
Option 3: I did not have room to stack a full size washing machine on the existing wall where the old washer and dryer use to be because I only have 32 inches of depth space and I believe even if the gas vent was boxed recessed into the wall you would still need an addition 4" clearance from the wall to the dryer? IF this is not correct this option would work than.

It might be possible to reuse the existing vent.  It depends on the construction of the walls and ceiling. There are specific, code mandated limits on cutting/notching/boring ceiling joists that must be followed to avoid damaging and weakening them.  

Making long pipe runs is difficult due to slope considerations. The vent line for a washer is supposed to be a minimum of 1-1/2 inch inside diameter pipe and must slope a minimum of 1/8th inch per foot back toward the fixture it is venting.

All of this work can be done.  The slab floor just makes it harder.  Sometimes compromises need to be made for function & code compliance over esthetics.


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Dana Bostick


Pretty much any residential plumbing questions. For "item specific" details such as a specific model of fixture, I will need to research and there may not be any useful information available. Note: I live and work in Southern California. We do not, as a rule, use hot water or steam heating systems, oil fired boilers or private water wells so my knowledge in those areas is pretty limited. There are others here on AllExerts that can probably answer those questions better.


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