Toilets, Sinks, Showers, Tubs and Disposals - depth of flanges/drains in concrete slab
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morework
11-22-08, 02:24 PM
Hello
A great wealth of knowledge here... here is my problem
The cottage currently has the bathroom plumbing routed on top of the concrete slab with 2x6s to support the floor. This results in an awkward 10" step up.
The plumbing drains to a septic system. This full bath is the exit point. From what I can tell is the waste pipe to the septic sits on top of the concrete and goes into the slab.
When the cottage was renovated there was a two inch differential in the floor of the existing and new structure.
We plan to level the concrete slab and at the same time would like to correct the step up problem.
Given that we will be adding to the 2-3 inches of concrete how much deeper do we need to go to for elbows, flanges, traps etc to reach a level surface?
I am worried about changing the pitch of the waste line as well.
Also should we locate the supply line in the floor or keep them above in the attic? This a cold climate.
Thanks for any advice.
A great wealth of knowledge here... here is my problem
The cottage currently has the bathroom plumbing routed on top of the concrete slab with 2x6s to support the floor. This results in an awkward 10" step up.
The plumbing drains to a septic system. This full bath is the exit point. From what I can tell is the waste pipe to the septic sits on top of the concrete and goes into the slab.
When the cottage was renovated there was a two inch differential in the floor of the existing and new structure.
We plan to level the concrete slab and at the same time would like to correct the step up problem.
Given that we will be adding to the 2-3 inches of concrete how much deeper do we need to go to for elbows, flanges, traps etc to reach a level surface?
I am worried about changing the pitch of the waste line as well.
Also should we locate the supply line in the floor or keep them above in the attic? This a cold climate.
Thanks for any advice.
plumbingods
11-22-08, 04:01 PM
Hello, and Welcome to DIY
I think I understand what you are trying to do is remove the step up and put the plumbing in the slab.
You will need approximately 8" from finished floor to bottom of trench at the flange, with the flange resting on the finished floor. I am figuring this with 3" piping which is all that is needed for the house. You may need to increase to 4" when it goes out the foundation.
From the flange, you will need a minimum of 1/8" per foot of downward pitch going toward the septic line. !/4" per foot is recommended, but 1/8" is legal for inside piping 3" and larger.
The smaller 2" and 1-1/2" pipes must be a minimum 1/4" per foot pitch.
So if you are putting in 3" pipe from the flange to the foundation/septic pipe and that distance is 10', you will need a trench 8" deep at the flange and a minimum of10-1/2" at the foundation/septic pipe. That measure is to bottom of pipe, so you need to check the depth of the existing pipe to see if you can go that low. If not a raised floor will be needed as was done previous.
I think I understand what you are trying to do is remove the step up and put the plumbing in the slab.
You will need approximately 8" from finished floor to bottom of trench at the flange, with the flange resting on the finished floor. I am figuring this with 3" piping which is all that is needed for the house. You may need to increase to 4" when it goes out the foundation.
From the flange, you will need a minimum of 1/8" per foot of downward pitch going toward the septic line. !/4" per foot is recommended, but 1/8" is legal for inside piping 3" and larger.
The smaller 2" and 1-1/2" pipes must be a minimum 1/4" per foot pitch.
So if you are putting in 3" pipe from the flange to the foundation/septic pipe and that distance is 10', you will need a trench 8" deep at the flange and a minimum of10-1/2" at the foundation/septic pipe. That measure is to bottom of pipe, so you need to check the depth of the existing pipe to see if you can go that low. If not a raised floor will be needed as was done previous.
morework
11-22-08, 08:05 PM
Hello, and Welcome to DIY
I think I understand what you are trying to do is remove the step up and put the plumbing in the slab.
...trench 8" deep at the flange and a minimum of10-1/2" at the foundation/septic pipe. That measure is to bottom of pipe, so you need to check the depth of the existing pipe to see if you can go that low. If not a raised floor will be needed as was done previous.
Thank you so much for your input. I was hoping I did not have to go that deep. I wonder how long it would take to bust up that concrete with a jackhammer?
I thought I might get away with using a shallower offset flange. Guess not.
The line to the septic does it have to be a straight run or can I introduce an elbow to compensate for the distance in height?
And is it ok to encase the supply lines in the concrete? I was going to use white pvc and wrap that in pipe insulation.
I think I understand what you are trying to do is remove the step up and put the plumbing in the slab.
...trench 8" deep at the flange and a minimum of10-1/2" at the foundation/septic pipe. That measure is to bottom of pipe, so you need to check the depth of the existing pipe to see if you can go that low. If not a raised floor will be needed as was done previous.
Thank you so much for your input. I was hoping I did not have to go that deep. I wonder how long it would take to bust up that concrete with a jackhammer?
I thought I might get away with using a shallower offset flange. Guess not.
The line to the septic does it have to be a straight run or can I introduce an elbow to compensate for the distance in height?
And is it ok to encase the supply lines in the concrete? I was going to use white pvc and wrap that in pipe insulation.
plumbingods
11-22-08, 10:43 PM
Good Morning:coffee:
The reason I say 8" to start is from memory of a 4x3 pvc closet flange and a 3" street 90*. (which is the shortest bend available unless you cheat and use the street 90* from a 3" pvc p-trap, which is actually not to code and is only a difference of probably an inch + or - ). I could be off a little, but not enough to worry about.
The concrete should only be about 3-4 inches deep, so you would need to remove it all, no matter how far down you want to be.
Long sweep 90* or 45* fittings are acceptable fittings for any offsets needed.
Like I said, the concrete is only 4" deep, so you will be running the supply pipes in the dirt and then coming up through the concrete to get above the floor. I don't think regular pvc is allowed for water piping, but CPVC is. If using a glue bonded pipe and fitting system, make sure to glue the fittings real good, let dry and pressure test before pouring the new concrete. Personally I would use sPEX piping underground with no fittings, but then you would need the tool to work with.
The reason I say 8" to start is from memory of a 4x3 pvc closet flange and a 3" street 90*. (which is the shortest bend available unless you cheat and use the street 90* from a 3" pvc p-trap, which is actually not to code and is only a difference of probably an inch + or - ). I could be off a little, but not enough to worry about.
The concrete should only be about 3-4 inches deep, so you would need to remove it all, no matter how far down you want to be.
Long sweep 90* or 45* fittings are acceptable fittings for any offsets needed.
Like I said, the concrete is only 4" deep, so you will be running the supply pipes in the dirt and then coming up through the concrete to get above the floor. I don't think regular pvc is allowed for water piping, but CPVC is. If using a glue bonded pipe and fitting system, make sure to glue the fittings real good, let dry and pressure test before pouring the new concrete. Personally I would use sPEX piping underground with no fittings, but then you would need the tool to work with.