Shower Drain Offset

[wwhitney]

How thick should the covering layer of actual concrete (is that called a "cap" ?) be after refilling the plumbing hole with all the dirt I took out of the hole in the slab ?

How thick is the rest of your slab? 3.5" - 5" is most common. Looks like your slab edges are quite rough, so it would be reasonable to skip adding any dowels to tie the patch into the existing slab.

Do I just add back the dirt in layers, and if so, how thick should each layer be, and compact each layer up to level from answer to question above ?

Yes, maybe 4"? Not too sure on that one.

Take care to avoid a gap under the pipe by tamping to either side of the pipe as you fill up alongside of it. Same for the edge of the existing slab. If your riser is perfect, avoid shoving too much soil under it as that could shift the pipe. You can tamp with a 8x8 flat plate, or for smaller areas, the end of a sledge hammer, or even a 2x4 on end that you hit with a sledge hammer. Avoid any rocks in the backfill in the vicinity of the pipes.

Cheers, Wayne

 

[NorthTexas]

Hi Wayne - thank you for your help.

The regular part of the slab is 5" thick and there is a concrete beam right there on the right side of the hole so that's crazy thick.

So should the new concrete "cap" be 5" thick ? I thought it wasn't supposed to be that thick so it could be "easily" broken out if a future homeowner wanted/needed to, no ? When I decided to remove the tub I sure was glad that concrete "cap" was there to get to the plumbing more easily.

In a YouTube video the guy coated the slab edges with thinset to help bond the old and new concrete - should I do that ? Or use another type of concrete bonding agent ?

Thanks again.

 

[Sponsor]

 

[NorthTexas]

Ok, plumbing is all in and glued up, looks good. Will let this setup for now.

I'm sorry but I am still confused about filling the hole back in.

Some YT videos use sand, dirt, crushed stone (3/4" I believe), etc., so which is best ? I would think having stone on top of and along side the pipes would be bad, no ? And do I fill with whatever material up to the bottom of the 5" thick slab and then add 5" of concrete, that seems like a lot of concrete, again on the pipes, no ? Or should it be just a very thin layer of concrete, if so, how thick is very thin ? With just a thin layer will there be enough strength and stability support for the pipes and the 1/2" - 3/4" of SLC that goes on top of entire slab area there ?

Sorry for all the questions but just want to do it right, so thank you all for your help.

 

[GReynolds929]

Sand or dirt is fine, no rock unless it's pea gravel. Concrete doesn't need to be thick, just a cap to keep unwanted creatures and vapor out, 1"-2" is fine.

 

[NorthTexas]

Thank you all for suggestions for filling the hole, I appreciate you all very much.

 

[NorthTexas]

ROOKIE MISTAKE !

So I was so excited this morning after getting the drain done... BUT... I forgot that the Kerdi drain has 3 1/2" of extra under it, the sloping piece and the tail. So the top of my my plumbing was too high for it... errrrr, raza fraza, son of a beep, @#!*&!! ...

BUT WAIT... the plumbing Gods gave me a one-time special dispensation - YAY !

I cut the long piece of straight pipe between my two 45s off, leaving about 1" of it sticking out of the hub of the street 45 that goes into the trap. To that I connected a 2-hub 45 to get me to 90, and to that a short street 90. That leaves the top of my revised plumbing about 3" below the tail of the Kerdi drain, so all good now.

Not the best setup, but will certainly work. Schideular-Kerdi does make the same drain with a 90 right off the bottom of it, so, kind of like that now but with a little tail piece before it.

Am I still okay with my new drain configuration ?

Thank you for you help !

 

[wwhitney]

Am I still okay with my new drain configuration ?

I mean, it works, but the extra 90 is inelegant, and the more horizontals you have between the shower tailpiece and the traps, the more places there are for debris to get stuck and microbial growth to cause odors.

In your last picture, it looks like there would be plenty of room to move the trap u-bend inlet to the left, so that you achieve the same additional leftward offset with a shorter section of pipe between the two 45s, allowing you to get to the desired drain location (in plan) at a lower height than your first attempt, but still with just your original two 45s. Would that work?

In other words, if you come out of the kerdi drain with a street 45a and stick a short piece of pipe in the street 45, and try to put your drain in the desired final location, can you? Or does the remaining concrete beam that you don't want to touch get hit by the street 45 and or the short pipe stub before you can lower the kerdi drain to the desired elevation?

If it does work, there's something to be said for cutting off the trap, adding a horizontal coupling, and redoing everything. Obviously nobody likes to redo work, but doing it the second time should take half as long (maybe an exaggeration, but not by much).

So if moving the p trap will work, it's up to you whether using the extra 90 is an acceptable compromise or not.

Cheers, Wayne

 

[NorthTexas]

Thanks so much Wayne.

I don't want to cut the trap out again given the difficulty to get a straight cut on its connection to the drain pipe, and since this meets Code, I'm going to stick with it.

A "good" thing about the 90 is that since it is up top there it should be easier to keep clean, i.e., just remove drain grate (it comes right off with that little Kerdi hook) and hit it with a flex-head cleaning brush.

I did a leak test this morning by putting a garden hose into the top of the new drain setup = no leaks, and made sure the trap is holding water as well using food dye and borescope = good to go.

Town building inspector will be out this week to sign off on plumbing rough-in.

 

[wwhitney]

given the difficulty to get a straight cut on its connection to the drain pipe

Well, if you ever have to cut the trap off and preserve as much pipe as possible on the outlet side, seems like you could use the trap outlet hub as a guide for your cut. E.g. run your blade (probably an oscillating saw) around the downstream edge of the hub, or perhaps on the hub side of that edge, on the assumption you could refine the cut anywhere you end up leaving a little bit of hub, and the remaining hub would would be a further guide.

Cheers, Wayne

 

[NorthTexas]

Thanks Wayne.

The issue is not the length of drain pipe left, there is plenty, but it would mean having to chop out more of the concrete slab to get to the trap hub to drain pipe connection (for an easy straight cut along the edge of the hub).

 

[wwhitney]

it would mean having to chop out more of the concrete slab to get to the trap hub to drain pipe connection (for an easy straight cut along the edge of the hub).

Pretty sure you'd have options to make the cut without breaking out more concrete. E.g. if an oscillating saw would be obstructed, you could use an internal pipe cutter (little circular saw on a Dremel, say) for the final cut. Just FYI.

Cheers, Wayne

 

[NorthTexas]

Thanks Wayne.

Really no other options other to bust out more concrete. I have an internal pipe cutter but it wouldn't work because even if I cut the 7" shaft to shorten it, the drill wouldn't fit in the hole.

 

[NorthTexas]

1. What size rebar should I use to help support the concrete patch fill in my drain hole ?
   
   
2. Does each piece of rebar need to be anchored into both sides or can they just be attached to 1 side of the hole (dowels) ?
   
   
3. Or do I use dowels anchored into 1 side of the hole and tie them together side to side with rebar ties ?

Thanks so much.

 

[NorthTexas]

Town inspector approved plumbing rough-in this morning.

Hole ready to for concrete, which will be Quikrete 5,000 psi, ~ 4" thick.

1. Used cushion sand (aka bank sand) under and around piping, compacted in 2" lifts with water spray.
   
   
2. Added a 2" top layer of #57 3/4" crushed gravel, compacted with water spray.
   
   
3. Covered with 10 mil heavy-duty plastic as moisture barrier.
   
   
4. Added several sticks of #3 rebar in 4" deep holes secured with Quikrete high-strength anchoring epoxy.

 

[NorthTexas]

Hole filled in, looking good. I used a slurry of the concrete to bond the old to the new.

How long do I need to wait until I put down the LevelQuik RS SLC ?

 

[wwhitney]

How long do I need to wait until I put down the LevelQuik RS SLC ?

Check the datasheet for that product.

Cheers, Wayne