If that is the case then you can use one method that is called "the pipe boot".

If, for example, you are going with a *four inch pipe, you cut a two inch diameter hole in the liner.
(NOTE.For whatever size of pipe you are going to use, the hole cut in the liner is half of that pipe's outside diameter)
. You then push the pipe through the hole in the liner and you will see that the liner around the hole hugs onto the pipe.
* Greg Bickel method of pipe boot.

The liner is then secured to the pipe with a 4" hose clamp (available at Home Depot/Lowes or any good hardware store).
Try and purchase a hose clamp with a stainless steel screw if you can.
The regular hose clamps are made from stainless (unless they are from Asia) but for economic reasons, they use a mild steel, tightening screw, that will eventually rust out.

If you cannot find one with a stainless steel screw don't panic, just smear the mild steel screw with a dollop of Vaseline to seal it from the water.

Once you have the pipe through the liner penetration hole and clamped where you want it. You then cut a piece of spare liner,overall 6 inches in diameter with a 2 inch diameter hole in the center of it.
This is the covering "doughnut" that will slide over the pipe and snug over clamp and the liner penetration point, to keep everything nice and neat.
(NOTE. Again the "doughnut" covering ring is sized to suit the pipe size used)

Greg Bickel, who used to contribute great ideas free to this forum some years ago, has a pond business now and sells a video CD Rom, about installing a pond, plus many other great ideas and tips.
The video includes a step by step series of pictures on the "Pipe boot" installation. I think Greg now charges about $10 for the video and that's a bargain for all the information it contains.

I should add, that you can purchase pre-molded pipe boots to suit different pipe sizes, from various sources on line, they can cost up to $100.

I hope the link to Greg's site works for you. I think there was a difference of opinion between him and the powers here at GW and they would not link to his site for a while.
You can just Google it if it does not work.

Hope this helps,
"Horton"

I dare say, though I have not tried it myself, that you could join PVC liner to EPDM liner by using EPDM liner splicing tape. It sticks solidly to any smooth surface it contacts, so I don't see why it would not stick to PVC liner.
I'm surprised that Mike has not responded to your question as I'm sure he would have the answer.
Sorry about the mix up,
"Horton"

Can you use EDPM liner splicing tape to seam both liners. It might work for a short time but I wouldn't use it. PVC liner has a life span of about 10 years where EDPM has a real life span of about 50 years. PVC liner is stiff and becomes brittle with age and isn't going to move with the EDPM liner. The joint will fail. Can it be done? Yes but I wouldn't do it. 10 years is a short period of time and it flies by.
Mike

Tavy, good luck with your project. You seem to have the right approach to the task at hand by researching out information before you get going.
I'm sure everyone will look forward to reading about your experiences and seeing the end results.
"Horton"

Horton, At my age 10 years just seam to fly by.
Mike