drain pipes embedded in mat foundations

[cliff234]

Does anyone have any experience allowing installation of drain lines in mat foundations? We have an 8' deep mat and the mechanical engineer is asking if they can run a 6" or 8" diameter sloping drain line through the mat. I have never before permitted this, but in this case we don't have too many other options. We would have control over where the pipe was to be located and we would locate so that it does not compromise the strength of the mat - and we would add additional reinforcing steel around the drain for crack control. My biggest concern is the problem we would have if the pipe leaked. Perhaps we could require the pipe to be pressure tested before the concrete was poured. We will discuss this with the mechanical engineer. I think the drain line is for floor drains. It is not a sanitary drain that would have a constant flow of water.

 

[SlideRuleEra]

Cliff234 - The thick mat foundations for the "plant island" (turbine/generator & boiler) of a steam electric generating station have numerous pipe lines embedded. Some are drains, others are pressurized for lubricants, compress air, fire protection water, etc. This is common practice in that industry. As you suggested, pressure test the lines for leakage before the concrete is placed.

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[KootK]

The sketches below show the systems that I'm familiar with, some of which have used embedded piping successfully. Options two and five seem to be the most popular in my neck of the woods. The issue with embedded piping seems to be less structural and more schedule. With embedded pipes, the plumbing design has to be set in stone before the raft is installed. And nothing can change during construction. Or during service for that matter.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[hokie66]

Embedded pipes in a thick mat do not present a structural problem, but it is usually necessary to provide flexibility in connections where the pipes enter and exit the mat. Make sure there are adequate cleanout provisions.

 

[Splitrings]

A welded HDPE pipe might be a good choice. Its flexible and you have no joints to leak.