Hello,
I am in the process of sealing the slab in my house with a product claiming to greatly reduce radon gas by sealing the concrete. It also reduces mositure. Since I have a bit of both I hope this RadonSeal will work. While tearing up the carpet and preping the floor (scarifing , cleaning it), I noticed that the adjoing bathroom has a hugh hole for the bath drain (a dap out?). I any event- it occurs to me that all this sealing is a big wast of time and money since this hole (that, from what I can see through a hole I made in the drywall), is big enough ot let water and gas through big time...

I don't think I should fill this hole with concrete since it may need to be serviced. Thoughts? Thx, GR

"I can see thru a hole I made in the drywall), is big enough ot let water and gas thru big time....
I don't think I should fill this hole with concrete since it may need to be serviced. Thoughts?"
This "hole" you made in the wall behind the dap-out should have been made by the drywallers and framed and paneled. It's called a "tub access panel" and is put there as a matter of course so the tubs drainage can be serviced.
In my area, (Tampa Bay), if there's a concern about termites the roof man will pour hot tar on the floor of the dap-out sealing it off. While I wouldn't fill the hole completely, from a plumbing standpoint, it's acceptable to cement up to just under the connection from the trap to the tailpiece of the tub shoe tee. From there you may radon proof away. Good luck, Tom

Tom-
Hello again (thanks for such a speedy response to my 1st about dap out/sealers and radon.

In my last I expained about a dap out that I intend to fill with concerete. You said to fill up below the 1st connection. Now that I've opend the wall up to install a real tub access panel - I notice another PVC coming out of the dap out, located about 2" toward the wall (not toward the tub), under the slab, and doing a 90degree than heaing over toward the sink- but not idea whare it actually goes. Is it OK to pour concete on this? It's a sealed conncection.

Near all this (in the wall), is another pipe coming straighht up out of the wall plate: and ending with a fixture labeled - Warning: serer gases do not remove. It lloks like they had a pblm with all this, and installed a fix (to vent or get air to vent). I really have not idead- jhust guessing.

I have issues this the toilet in this room- and have no confidence that the plumbing is good in this 8yo house. WHen the washing machine (right above) drains, the toilet bubbles- (thus maybe the explanation for the in-wall air vents. Of course they don't seem to work since the toilet still bubbles.

Point- you still feel it OK to fill the dap out... Sorry for the length!!

"you still feel it OK to fill the dap out?"
That sounds like they added a vent to the tub. It'[s OK to fill it up to the compression nut on the trap raiser in case you ever have to change out the tub waste assembly.
You toilet bubbling's another story. If this just started you have a partial blockage in the drain line that's sending back pressure back up the line. Hense, the bubbles in your toilet. The solution is to snake out the drain from the washer vent or the bathroom lavatory vent. If not the washer pump's just too powerful for the system. Good luck, Tom

[QUOTE=speedball1]"
You toilet bubbling's another story. If this just started you have a partial blockage in the drain line that's sending back pressure back up the line.

The bubbeling has been their since day 1. (a new house). The line had been snaked already. They could not figure it out. Any other suggestions?

"The bubbeling has been their since day 1. (a new house). The line had been snaked already. They could not figure it out. Any other suggestions?"

Yes, a few.
If the trap and standpipe were 1 1/2" or even at 2" the more powerful pumps of the new washers could overpower the system with the volume of the discharge. This has happened twice with new Maytag washers on this page.
Both times Maytag replaced the culprit with a washer with a pump that wasn't as forceful. It may not be in your system at all.
If all that happens is a little bubbling in your toilet then the problem will remain minor unless you develop a partial clog in the drain line and it begins to back up out of the stand pipe or in a lower fixture such as a shower or a tub.
If the situation gets worse, click on back and we'll address it. Regards, Tom