Radical plumbing

In the Create an Oasis with Greywater book, the author discusses "Radical Plumbing" in chapter 4. This is basically connecting each sink/tub drain directly to 1" or 1 1/4" HDPE pipe and sending that to the landscape, without any joints or splits.

I've tried to locate the fittings that would connect the 1 3/4" sink drain male threads to a 1" or 1 1/4" HDPE pipe and they don't seem to exist, so I'm not sure how someone would implement this.

Does anybody know how to connect HDPE pipe to a sink drain?

Have you looked into rubber couplings?


https://www.menards.com/main/plumbing/rough-plumbing/pipe-tubing-hoses-fittings-accessories/fittings/flexible-fittings/flexible-standard-couplings/4-x-2-ci-plastic-x-ci-plastic-co/p-134668-c-9368.htm

John Wolfram wrote:Have you looked into rubber couplings?

Great idea. I'll try connecting a 1-1/2" plastic downtube to the 1-3/4" male threads, and then connect it to the 1-1/4" HDPE with a 1-1/2" to 1-1/4" rubber coupling. Thank you!

It may be possible to enlarge the internal diameter of the HDPE pipe by heating and manipulation and insertion an object of the same diameter of your sink drain pipe. You can then clamp the HDPE pipe directly to the drain pipe with a ring clamp. Clamping while the HDPE is warm will ensure a good seal. I have used a heat gun in the past for similar applications, try not to overheat and do all heating in a well ventilated area.

P Lyons wrote:It may be possible to enlarge the internal diameter of the HDPE pipe by heating and manipulation and insertion an object of the same diameter of your sink drain pipe. You can then clamp the HDPE pipe directly to the drain pipe with a ring clamp. Clamping while the HDPE is warm will ensure a good seal. I have used a heat gun in the past for similar applications, try not to overheat and do all heating in a well ventilated area.

I like this idea, since it doesn't involve reducing the size of the drain, which could lead to clogs. The 1-1/2" HDPE pipe that I found has an actual inner diameter of 1.61", so it would probably fit over the downtube without being stretched. Would a clamp tighten it down enough to create a seal? Possibly with a heat gun? Or should I order the 1-1/4" pipe, which has an inner diameter of 1.25"? Thank you.

See if it is possible to get a small sample of each pipe size, then you can test to see which option is the best fit before you purchase. You could also bring the sink drain with you to the store to test there. As for the seal you just need enough pressure to ensure that friction holds the pipe securely in place, so a little heat on the 1.5" line should be fine. With the drain from the sink inserted within the HDPE line, water will follow its natural path downhill. Any leaks would indicate that there is a clog in the line.

If all I really need is the friction to hold the pipe in place, I think it would be easiest to make a small cut down the end of the tube and overlap the tube walls where I clamp it. Thanks for the ideas. This was very helpful.