1 1/4 inch waste pipe in concrete

lomb

I have solvent welded high quality waste pipe buried in concrete directly -3 inch floor screed without expansion joints. Approx 3-4 meter runs. Ive connected it to a commercial dishwasher that discharges waste water at around 70 degrees. I intend for this to be used 4-5 times a day.Is there a chance of cracking and failure over the years from expansion/contraction. What was the proper way if any to do the above . It needed to be run below the surface and there was only 3 inches to do it in so directly screeding was what the builder did. Im not too worried on the rest just with the high temperature discharge is likely to expand /contract it. Does it expand within it self?Thanks

Calahonda52

http://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html
may help
It may actually crack the screed near where it enters the floor

RJF

I don't think it will be a problem as the water will flow out of the pipe to the gully or main drain quickly enough to prevent any overall linear expansion of the pipe. This assumes a general regular fall on the pipe. Also the mass of concrete around the pipe should help dissipate the heat quickly if any water remains in the pipe.

You could also turn the dishwasher to a cold or at least lower temp wash immediately after. Just allow it to fill with water and then drain it if this is possible.
If it is not, then maybe run a cold water feed to the waste pipe with an air gap and with a valve/tap you can turn on at the end of wash cycle.

If you wanted to go the whole hog put some sort of thermal or flow switch on the waste to turn on the cold supply any time the dish washer drains. Wouldn't be that hard or expensive to do.

lomb

Thanks Il look into the autodrain cold mix option Ive heard of this before. At least I know there is no immediate issue. I believe a fall was put in at the time and certainly after 3 meters the water drops 3 foot down into the large toilet drain soil pipe.

RJF

If its only going three meters don't even worry about it. From your original post I got the impression it was going a long distance with a number of "3 - 4 meter runs" joined together and you were worried about a section parting.

lomb

No worried about the pipe cracking within itself as it cant expand as its restricted by the concrete. Theres very few joints I made sure of a straight run as far as I can remember. Im wondering if he should have wrapped it with something like insulation to allow an expansion space? Then again I think cement gets hot when it sets? So did the pipe expand while it was setting and then contract to leave a space?

RJF

no worry about expansion on the diameter. Distance too short