Under the sidewalk pipe boot fitting

[gardengimp]

Seeking input ....

4" Sch 80 PVC pipe drove under the sidewalk about 9 months ago to connect the ponds on either side. Our native soil is sand, and this particular spot was heavy with roots. Very old very large stump found digging the initial side pond. Driving the pipe under the sidewalk entailed lots of root removal. The sidewalk is 30 years old, and one section has already tilted due to tree roots.

When I did the first side of the pond, I followed instructions I found online to do a pipe boot fitting using your liner and a hose clamp. That worked OK, not great, but OK until we had 10 inches of rain in 5 days. Then it leaked badly. To repair the leak, I filled as much of the vacuum I could with sand. Watered to settle it. PL gooped, the heck out of the pond side of the joint all around the hose clamp. Took special care with the tip of the hose clamp which looked to possibly have worn a pinprick hole in the liner. Then filled the back side of the cavity with non adhesive super gooyey and runny roofing asphalt. It made no sense to me to try to form a horizontal pipe in concrete.

Now I need to do a pipe boot on this side. I've picked up an Oately Thermoplastic Roofing Flashing (for roof vents) that I can install over the pipe. Then fill in securely behind the flashing. The front side of the flashing will give me a secure surface to PL goop the liner to. At least that's what I think.

Once the liner is in place, glued, secured, and I cut a hole in the liner - I plan to use a flexible 4" x 4" connector to both secure the epdm to pipe connection and to extend the pipe opening a few inches.

So, is this is good plan? How can I make it better? And, will PL Roof & Flashing sealant even adhere EPDM to thermoplastic?

 

[DrCase]

Why couldn't you use your rubber 4x4 connector attach a 4" toilet
flange on the out side and a 4" toilet spacer on the inside.
the spacer is just the ring with out any pipe attached . than bolt them together with the liner between

 

[gardengimp]

Hmm, I looked at those when I wondered around looking for ideas. You put screws through the liner? Do you goop one side first?

Would you leave some play around the connection to allow for movement and settling?

 

[Waterbug]

Like DrCase said, a mechanical bond is needed. I've never used a toilet flange for this, but I can certainly see that working. Could be better than the pipe boot.

I do like the pipe boot personally and would just work on getting better at installing one. It is tricky. I'm not sure why yours failed. After the clamp is on I wrap the entire clamp in a 1" strip of EPDM so the liner doesn't get pushed onto the sharp metal. I don't think goop would offer much protection.

Applying goop to the outside of the pressurized water (which you have even if very low pressure) depends on the the bond the goop makes to the two surfaces (pipe and liner). I doubt the goops mentioned are rated to do the job. But telling people about the downside of goop seems to just annoy people so I'll stop there.

 

[gardengimp]

For the record, PL Roofing and Flashing Sealant does not adhere to thermoplastic. Might be a good way to make gaskets though; it peeled off as easy as could be.

I agree that pipe boots is a practice thing. I should probably practice on scrap pieces of epdm laying around. Get the hang of where to make the X. As for why mine failed? Just guessing at a few probable causes: (1) it was my first (2) I should have filled the pond and let it all settle before making the cut (3) I should have left some slack in the liner around the pipe area and lastly, when we had the 10" of rain in 5 days, there was a lot of settling and stuff under the pipe. I found a small rip in the liner on the top side of the pipe. I'm going to use the roofing flashing thing on this side I'm working on now; I'm using the flashing mostly as a means to drive and compact the sand on what will be the back side of the liner. The flashing will give me a form to compact the sand against. Sure I could have fabricated something, but for $4 this already fits perfectly.

This time around, I'll let the liner and pond settle before I go cutting the hole. Now I have to decide on the pipe boot or the flange. Gad zucks, whose idea was this to connect two ponds under the sidewalk??? Sounded pretty simple at the time.

Ah, I've been wondering what you where referring to when you said "applying goop to the outside of the pressurized water ....". When I fixed the leak, I had a void zone that I couldn't get to easily where sand had traveled off in the heavy rain. And traveled off more with the leak. I couldn't get UNDER the pipe to pack the sand and I didn't know how far the void spaces went under the sidewalk. I could get sand on top of the pipe through the rotted out expansion joint in the sidewalk, but I couldn't get sand packed around the pipe as it passed through the liner. So I decided to using roofing asphalt. My thought was that it is runny enough to run into all of the void spots, viscous enough to build up around the pipe, and even though it wouldn't seal to the liner or pipe, it would be a water resistant zone around the pipe/liner connection. Did it work? /shrug. It is not currently leaking enough to be noticeable. I am however, planning to pump down that side of the pond to fill part of the new side so that I can open up and check that pipe connection. I'm curious to see what it looks like on the backside.