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Water under basement bathroom floor

My home is a tri-level with the basement being just a few feet below grade. I am remodeling a bathroom in the basement. Once I gutted the room and removed the existing tub, I found a plywood floor on 2x8 joists. The rest of the basement has a concrete slab. Below the joists in the bathroom, I see water. I haven't yet removed the plywood to figure out what (if anything) is supporting the joists. The PVC tub drain seems loose to me so there may be a leak in a pipe. The water could also be ground water. I don't have any odor so maybe the pond of water is acting as a giant trap.

How do I proceed? Should all the lumber be removed, correct the PVC drain pipe, and then pour concrete in the space? The room is about a 7' cube. The house was built in 1962, but the bathroom was added later. I plan to hire professionals for the plumbing and a new floor but I want to understand what I am asking them to do. I want to replace any galvanized or cast iron pipe with PVC.

The supply lines are under the floor submersed in the water. The wall where the sink and toilet will be located are cement block the first 24". Instead of routing new copper under the floor, I am thinking of using PEX routed through the ceiling. Will PEX fit behind the drywall with 1/2" furring strips between the drywall and the block wall?

Re: Water under basement bathroom floor

Keep ripping things apart until you find the source of the water.

Re: Water under basement bathroom floor

I'm interested to find out why you have standing water there too.

I suspect that you are going to find a few more questionable things there. Before you invest more money, get the proper answers to those questions.

Re: Water under basement bathroom floor

Forget the rest till you deal with the water under the floor. If it's groundwater you will be well served to pour a concrete floor with special attention paid to waterproofing the edges so there are no seeps. I prefer PEX wherever I can use it these days with the heavy crimp rings- not the kind where you crimp the bulge on the side. It can be run under concrete with no worries, but you don't want copper and concrete together as it will corrode. Running PEX supplies under the floor will be OK. If you want those in the walls I'd prefer they not be run directly under the drywall- someone may want a bracket or picture there later and pierce the pipe. Perhaps you can route PEX inside the block and fish it out at the bottom.

One issue you may run into is that most concrete outfits have a minimum charge- usually 5 cubic yards- and you won't need that much concrete. Alternatives will be a lot of hand-mixing or possibly renting a concrete (not mortar) mixer. Or you or a neighbor may have other projects in mind which will use the rest since you're going to have to pay for it anyway. Going back with a wood floor is not a good idea with the area enclosed over dirt- you will have problems doing that sooner or later but not with a concrete floor. Always replace galvanized but you can leave cast iron drains so long as they're in good shape and well supported- they'll last over 100 years like that.


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