Downpipes to travel under slab to get to rainwater tank.

[Eric bardon]

Greetings Knowledgable ones. I am designing a house which has all roof water going to rainwater tanks. The downpipes will go down to some kind of underground pipe then travel across to a nearby rainwater tank. One of these pipes must travel under a slab.
I think alot about the future of the house and don’t want pipes to die under the slab. What is the best kind of pipe (material wise) to use in this situation? how much of a fall will it need? ( It will travell about 3.5m under the slab)
The section of slab it will be under is actually external. Would it be a good idea to not cover the pipe with concrete and instead cover it with gravel/pebbles? thankyou in advance, Jo

[Retired plbg1Participant]

I would use PVC pipe and give it about 1/4″ per ft. fall. You could put wood form over trench where pipe is and pour concrete and when con. is set up take out form and then put expansion joints on each side and then pour that section and that way if you have troubel then you brake up con.

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Art retired plbg

[joleneParticipant]

Thanks for your reply! This is a cross section of what I think you mean. Is this a correct interpretation?

[Retired plbg1Participant]

Yes[img]null[/img]

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Art retired plbg

[nicktheplumberParticipant]

1)I would suggest embedding the pipe in some gravel, and not placing concrete around it;
2) I would suggest using polyethelene (first choice) or PVC or Cast Iron (second choice).

NtP

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