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Hydraulic Cement

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  • Hydraulic Cement

    I just finished the rough in for a basement bathroom addition and the only thing I have not done is seal the remaining hole I cut out of the slab to accomodate a shower drain p-trap. All the other sub-slab trenches have been patched using a standard quickrete bag mix. I have to say that I have never, and this includes several hundred slab tract homes, nor was I ever taught to, nor observed any other plumber, nor can I find anything in the code to require, the sealing of the hole in a slab left by a tub box (or in this case a hole created via demolition). However, in this case, the HO has a specific concern about hydraulic leaking in his basement because he routinely experiences some leaking through various cracks in his basement slab during periods of heavy rain. We have already discussed the need for an adequate french drain, he currently has no drainage system, but the HO has requested this hole accomodating the shower p-trap be sealed.

    Here are my questions:

    Does anyone else, under routine or normal circumstances, seal these holes?

    This, hydraulic leaking, being a known problem for this house, how probable, if at all, would leaking be at the joints of the concrete patch and existing slab, around pipes where they exit the slab, or around the in-ground sump that was installed?

    Is there anything better to use, for this purpose, than hydraulic cement?

    Has anyone experienced any problems from hydraulic leaking through unsealed slab holes?

    What is the best way to insure that this is never a problem for the HO?

    I appreciate EVERYONE'S input on this and if this turns out to be something that is common practice elsewhere, please don't give me any grief about it as I am already, suddenly, quite concerned that I may have left a trail of problems all around my area while working for both other companies as well as myself. I have never had any HO report any problems of this nature to me but it is just something that I never considered before. Thanks for your expert input.

  • #2
    The annular space around all pipes in slab voids including tub boxes (more common today) and shower drains (rarely done) are suppose to be mudded after you are done with them. Some inspectors do not realize this and will not call you on it but it can be a big problem for the homeowner. Not only can you get ground water coming through the slab but pest will also come through the slab as well. There is nothing like a colony of red ants living under your tub to ruin your day.

    A lot of guys just take a handful of cement out of a bucket and just put a skim coat in the void to fool the inspector. If the slab is a 3” slab you are suppose to put 3” of mud into the void.

    As for the patch leaking, if there is a lot of ground water you need to use a water resistant mortar and let the HO know that he may have to have a waterproofer come in when your done to try and seal any problems. These are all things you want to include in any contract which is in an area with a high water table and basements.

    Last edited by ToUtahNow; 06-28-2006, 11:20 PM.
    "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

    I never lost a cent on the jobs I didn't get!