# Forum Home Renovation Bathrooms  How to install a floor trap in existing concrete slab?

## whiteknightoz

We are looking at installing an ensuite into the master bedroom as the room is huge, the shower and P trap toilet will be along an external wall so no problems with the pluming there but whats the easiest way to install a floor trap in an existing concrete slab?   
also I need an p trap under the floor wast or can I run this straight outside with a flap on the end to keep the vermin out? 
Not sure what diameter pipe is required for floor wastes but I was thinking of using the angle grinder and cut two lines 50mm deep from the middle of the floor to the wall then jackhammer this channel out, place the pipe in the channel then screed over the whole lot to get the fall?

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## pawnhead

Since no plumbers have chimed in;
I think that 'dry' floor wastes are permitted in laundrys, but I'm not sure about bathrooms. They can't be connected to the sewer of course. 
Your idea with the channel sounds OK, but there might be a tendency for the slab to crack there. The alternative of cutting a slot, putting the dry waste below, dowelling the slab and replacing the section would be better I reckon, but it would still crack there if it wanted to go anywhere. 
Ripping it all up and pouring a new slab is the perfect, but expensive solution of course. 
I'd  go with option 2, and hire a wall saw that will go right through the slab. Then just lift the section out, but if you want to save hiring a saw, then your idea sounds OK.

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## Master Splinter

I've actually done the 'cut slab down to just before the reo and break the concrete out' approach - wasn't all that hard, and it meant that when I poured the patch there was the existing reo to hold it in place, so no mucking around with dowells.   
I did cut the reo in one spot to get some larger chunks out (and to make it easier to slip the pipe in) but a mesh offcut went over that easily enough.   
I made the cut about 250mm wide, to give me room to work and fiddle around and it meant that there was a good mass of wet concrete...I never like dinky little patches, they never seem to set right!

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## whiteknightoz

thanks for the replies..  Is there any advantage in putting the floor waste in the middle of the room as opposed to closer to the exterior wall hence less concrete cutting?

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## pawnhead

> Is there any advantage in putting the floor waste in the middle of the room as opposed to closer to the exterior wall hence less concrete cutting?

  There are advantages, but you don't have to put it in the centre.
Apart from the aesthetics (it looks better), it also means that the first course of wall tiles is level, since the fall is from the perimeter to the centre. Of course this is also an aesthetic consideration since the bottom course of tiles can easily be cut to a fall. 
Recommended fall is between 1:80 > 1:60 (for showers), but I've seen floors with much less fall than this. If it's not in a shower, then there's very little water that gets on a bathroom floor, and it's very difficult to get large tiles falling to a central point without cutting an X in the floor pattern so the whole floor is like an upside down pyramid with four edges cut from the corners of the room, to the central floor waste. If the grout lines are tight (1.5mm), then it's impossible to get the surfaces to line up perfectly, but the less fall, the less noticeable it is. 
In my new bathroom for example, I'm putting the floor waste very close to the door where the floor meets with the lounge room floor. The reason is that I'm chopping the joists down a little bit so that the floors are the same level without that aluminium angle step that you often see at a bathroom door threshold. If the waste is close to the door, then there's less timber I'll be chopping out of the joists. I'll just run the floor slightly uphill from there to the opposite wall. You won't notice that the floor is falling because I'll be using big tiles, so I'll put less than the recommended fall so the tiles will line up without having to cut diagonals in them. Something a bit less than 1:100.
There won't be any cement bed because I can't afford the height, so I'm packing and planing the joists to an exact fall (within 1mm), and I'm deflecting the Scyon floor sheets into a cone shape so I can glue the tiles directly to it (On top of a membrane. Although you don't need to waterproof joints in Scyon outside a shower, I will anyway). 
In my shower, I'm putting a smartile floor waste in the corner, and I'm making the floor absolutely flat so the tiles will glue straight down without any diagonal cutting, but I'm making the whole floor fall from the opposite corner, down to the corner where the floor waste is. I'll make this 1:60 so it gets good drainage. I'll start my wall tiles at the lowest point in the shower (which will step down 15mm from the floor outside the shower so the water stays in the shower cubicle), and I'll cut all the rest of the bottom tiles accordingly, so they are all dead level at the top. They'll be big marble tiles, so you won't notice that some of the bottom course have had 30mm or more taken off the bottom, on a very slight fall. 
The reason that I'm falling the shower to the corner, is because the door is at a 45 degree angle to the cubicle, so the floor will be absolutely level across the shower door step down. If it were a square cubicle, then I'd still make it level across the door, but obviously this means that it would also be level across the opposite wall that the floor is falling towards. In this case I'd use a stainless trough that goes right along the wall. They look good, and they're in vogue nowadays, but a nice looking approved model will set you back over $200. A Smartile (that you insert your own tile in, so it almost disappears into the floor. You can also get troughs that you insert your own tiles in so it just looks like two slots in the floor) only costs around $45, a chrome plated brass waste costs about $10, or if you don't care too much about peeling chrome, then you could get a cheap and nasty chrome plated plastic waste for a couple of bucks (not worth the savings I reckon. They just don't last that long before they're all scratched up). 
Edit; 
Actually a trough would be a good option in your case. It says on that ebay listing that the trough is only 19mm deep, so you could just bed it in so it ends up level with your tiles, falling to the outside. If you use a 'tile insert' model, then you'd just see two stainless steel slots, about 100mm apart from each other, running across your floor (but they're a bit deeper than 19mm so you might have to chop a bit out of the slab). That wouldn't look too bad actually. You could fall your floor in a Vee shape to the centre, or you could run it up against a wall (so it's right out of the way), and fall the whole floor towards it. 
That's the best solution if you don't mind spending a bit on the trough. It would look good, and there's virtually no slab chiselling to do. You'd also have a flat floor (much easier to lay the tiles) so there's no hassles with cutting diagonals if you're using big tiles and tight joints. :2thumbsup:  
Edit2;
You may have to block up the round waste hole in the bottom of the trough, if it's not long enough to be cut off. Since it's a dry waste, you could just poke it out the wall and leave the end open to let the water flow out (put some stainless mesh over the end so that roaches can't climb up into your bathroom for a drink of water), or leave the waste hole outside if it's at one end of the trough. Or just get a $tainless $teel guy to tailor make one up for you exactly how you want it.

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