What to fill tub/shower drain slab void

[Russell Harris]

Hi, just finished re-building two tub/shower drains that were cast iron p-traps in a slab foundation. I'm not sure the right terminology but the original 'pit' over each p-trap had solidified tar on in it. After getting the foundation soil back in place I was wondering what I should put back in place of the tar? One install will stay a tub and have it's drain. The other is becoming a shower only and I was thinking, should I just concrete/mortar up around the 2" shower drain pipe stub just like I would a toilet stub up? or should I keep it a 'pit' and do the same for both.
Thanks!
RH in Austin

 

[Reach4]

Hi, just finished re-building two tub/shower drains that were cast iron p-traps in a slab foundation. I'm not sure the right terminology but the original 'pit' over each p-trap had solidified tar on in it. After getting the foundation soil back in place I was wondering what I should put back in place of the tar?

You might want to make a sketch, because I cannot picture what you are describing.

You mention a trap and a pit. Are you saying there was a cover that you removed, and could then access the trap through the opening?

 

[Sponsor]

 

[RetiredInGueydan]

Hi, just finished re-building two tub/shower drains that were cast iron p-traps in a slab foundation. I'm not sure the right terminology but the original 'pit' over each p-trap had solidified tar on in it. After getting the foundation soil back in place I was wondering what I should put back in place of the tar? One install will stay a tub and have it's drain. The other is becoming a shower only and I was thinking, should I just concrete/mortar up around the 2" shower drain pipe stub just like I would a toilet stub up? or should I keep it a 'pit' and do the same for both.
Thanks!
RH in Austin

The pit is necessary to access the p-trap, just line the pit with plastic sheeting and fill with sand.

 

[Russell Harris]

You might want to make a sketch, because I cannot picture what you are describing.

You mention a trap and a pit. Are you saying there was a cover that you removed, and could then access the trap through the opening?

In the pic below, this is before work. Red arrow points to tub drain, p-trap is below in dirt. The tub drain and overflow sat over this area.

Outline in green was originally filled with hardened tar. At least that's what I guess it was. Shiny and black and very hard.
P-trap is now replaced. dirt is back in.
BTW, I did not cut that tension cable. It was done I assume in decades past by someone not too smart.

This is a 1970, single story, slab house in TX.
Thanks!

 

[Russell Harris]

The pit is necessary to access the p-trap, just line the pit with plastic sheeting and fill with sand.

Thanks RetiredInGueydan, I was wondering though, given that over one of these pits I'll be putting a custom built mortar bed with fiberglass lined shower and then more tile mortar and custom tile; how accessible is the P-trap really at that point? I mean busting out some lightweight mortar after having to go through all that on the shower? I mean, I plan on being 6' feet under myself when that happens

 

[RetiredInGueydan]

Packing the p-trap with sand and applying the lightweight mortar would do the job. You just never want anything but sand around the p-trap.