I am trying to replace all the plumbing in my house with PVC drainpipe. All the 'books' say to dry-fit the system to get the lengths and angles of pipe and fittings and to mark the joints with a "T" pattern marking the seam and fitting angle.

The same books say to use these reference marks when glueing the assembly, but ALSO state to insure that the pipe is FULLY seated in each fitting. The problem is that pipe will not fully seat in a dry fitting, so the lengths will be off when the system is glued and the pipe is fully seated.

The alternative would be to measure the length of pipe required to fully seat into the fittings and to use these longer lengths when glueing. The problem here however is that you lose all the angle reference marks.

My three questions are:
1) Given that this is drainage and not pressurized, how critical is it that the pipe be fully seated in the fittings? Most of my issues are with 1-1/2" and 2" pipe where I'm getting only about 1/2" of seating in the approx. 3/4" hubs.
2) Is there some other solution to this problem? In a simple system, I could fairly easily install a longer pipe. However, my assemlby is rather complex and runs through holes in joists, etc. with several fairly critical angles, so my reference marks are very important.
3) Do most "pros" really insure pipes are fully seated and, if not, how common are leaks in PVC solvent-welded systems?

Thank you all very much in advance for any help you may be able to provide.

1) "Given that this is drainage and not pressurized, how critical is it that the pipe be fully seated in the fittings? Most of my issues are with 1-1/2" and 2" pipe where I'm getting only about 1/2" of seating in the approx. 3/4" hubs."

Since the female PVC fittings are tapered if you fully seat them you're going to have a hard time pulling them apart to prime and glue them. I will explain the way we run PVC later.

2) "Is there some other solution to this problem? In a simple system, i could fairly easily install a longer pipe. However, my assemlby is rather complex and runs through holes in joists, etc. with several fairly critical angles, so my reference marks are very important."

OK, Here's how we do it. You'll need a magic marker to make reference marks on the pipe and fitting. We call a fitting that is seated one that is "made up". The measure is called the "make up measure".
Say we were roughing in a slab or a basement. First we lay the pipe in the trench and lay the fitting(1) on the pipe at the point we wish it to go. We then take a measure from the last fitting hub(2) to the make up,( bottom of the hub) of the fitting and make a mark on the pipe. We then cut the pipe to size. Now we a pipe that we will prime and glue to fitting hub(2). We then take the fitting(1) and slip it on the pipe UP TO THE POINT THAT IT BEGiNS TO BIND. And position it. STOP and mark both the hub and the pipe. Take the fitting off the pipe and prime and glue the fitting(1) lining up the two marks on the hub and the pipe. We then go on to the next fitting. I hope I've explained this so it's understandable and not confused you farther.

3) "Do most "pros" really insure pipes are fully seated and, if not, how common are leaks in PVC solvent-welded systems?"

We don't "fully seat" our fittings. Properly primed and glued there will be no leaks. All our drainage are filled from the roof vents the night before inspection and left overnight for the inspector to check next day.

Regards, Tom

My past experiences with PVC pipe that requires numerous joints is that I never seem to be able to get the lengths right so that all joints are fully seated. Dry fitting allows the pipe to go into the fitting only part way. I’m not sure that I totally understand your reply to the question about dry fitting PVC pipe. If I were to do an entire layout of pipe, fitting the dry pieces together to the point where the just become tight, then none of the joints would be fully seated. Is this correct?
Could you possibly rephrase or expand on your previous answer? It may clarify things a bit for me.
Thanks for you help
Ed

Quote:

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Originally Posted by speedball1

1) "Given that this is drainage and not pressurized, how critical is it that the pipe be fully seated in the fittings? Most of my issues are with 1-1/2" and 2" pipe where I'm getting only about 1/2" of seating in the approx. 3/4" hubs."

Since the female PVC fittings are tapered if you fully seat them you're gonna have a hard time pulling them apart to prime and glue them. I will explain the way we run PVC later.

2) "Is there some other solution to this problem? In a simple system, i could fairly easily install a longer pipe. However, my assemlby is rather complex and runs through holes in joists, etc. with several fairly critical angles, so my reference marks are very important."

OK, Here's how we do it. You'll need a magic marker to make reference marks on the pipe and fitting. We call a fitting that is seated one that is "made up". The measure is called the "make up measure".
Say we were roughing in a slab or a basement. First we lay the pipe in the trench and lay the fitting(1) on the pipe at the point we wish it to go. We then take a measure from the last fitting hub(2) to the make up,( bottom of the hub) of the fitting and make a mark on the pipe. We then cut the pipe to size. Now we a pipe that we will prime and glue to fitting hub(2). We then take the fitting(1) and slip it on the pipe UP TO THE POINT THAT IT BEGiNS TO BIND. and position it. STOP and mark both the hub and the pipe. Take the fitting off the pipe and prime and glue the fitting(1) lining up the two marks on the hub and the pipe. We then go on to the next fitting. I hope I've explained this so it's understandable and not confused you farther.

3) "Do most "pros" really insure pipes are fully seated and, if not, how common are leaks in PVC solvent-welded systems?"

We don't "fully seat" our fittings. Properly primed and glued there will be no leaks. All our drainage are filled from the roof vents the night before inspection and left overnight for the inspector to check next day.

Regards, Tom

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"Dry fitting allows the pipe to go into the fitting only part way. I'm not sure that I totally understand your reply to the question about dry fitting PVC pipe. If I were to do an entire layout of pipe, fitting the dry pieces together to the point where the just become tight, then none of the joints would be fully seated. Is this correct?
Could you possibly rephrase or expand on your previous answer? It may clarify things a bit for me"

What part of, "Since the female PVC fittings are tapered if you fully seat them you're gonna have a hard time pulling them apart to prime and glue them." don't you understand? I can't simplify it any farther.
I explained how we run PVC in detail. Please be specific about what it is that you don't understand and I'll try to explain it better if I can. Regards. Tom

My past experiences with PVC pipe that requires numerous joints is that I never seem to be able to get the lengths right so that all joints are fully seated. Dry fitting allows the pipe to go into the fitting only part way. I’m not sure that I totally understand your reply (quoted below)to the question about dry fitting PVC pipe. If I were to do an entire layout of pipe, fitting the dry pieces together to the point where the just become tight, took it all apart and glued it, then none of the joints would be fully seated. If you have a situation where you determine a relationship between 2 pieces where the position of one depends on the other, how would you go about setting everything up?
Could you possibly rephrase or expand on your previous answer? It may clarify things a bit for me.
Thanks for you help
OK, Here's how we do it. You'll need a magic marker to make reference marks on the pipe and fitting. We call a fitting that is seated one that is "made up". The measure is called the "make up measure".
Say we were roughing in a slab or a basement. First we lay the pipe in the trench and lay the fitting(1) on the pipe at the point we wish it to go. We then take a measure from the last fitting hub(2) to the make up,( bottom of the hub) of the fitting and make a mark on the pipe. We then cut the pipe to size. Now we a pipe that we will prime and glue to fitting hub(2). We then take the fitting(1) and slip it on the pipe UP TO THE POINT THAT IT BEGiNS TO BIND. And position it. STOP and mark both the hub and the pipe. Take the fitting off the pipe and prime and glue the fitting(1) lining up the two marks on the hub and the pipe. We then go on to the next fitting. I hope I've explained this so it's understandable and not confused you farther.

The ends of the PVC pipe need to be deburred before dry-fitting and glueing can take place.

Cutting plastic pipe with a wheeled cutter will leave an upraised ridge on the outside edge of the pipe, which will push the pipe cement out of the fitting when glueing.

Also, no clear glue or clear primer when gluing up your joints -- Most municipalities require purple primer (to prove primer was used) and a hot blue glue (a much better solvent weld than clear glues).

I do debur ID's with such a tool. I also roughen up the OD. Purple primer is used but I have never seen a hot blue glue at Home Depot Or Lowe's. Do you actually heat it? Deburring ID and OD still doesn't allow a bottom fit for pipe and I am wonder how you could dry fit an entire layout and expect to accomplish bottom fits on all joints.

I measured the depth of the female part and then marked the outside of the seated male where it met the female. If the mark was less than the joint depth, I just added the difference to the measured pipe length. This worked pretty well. I think this is what Tom said.

For turns, etc, I marked the dry fit with a Sharpie in two places so that it was easy to line up when cementing. Just be sure the alignment marks go beyond the portion that will be covered with the purple primer, which can erase the Sharpie marks.

Ed,
You're never going to be able to dry-fit the whole system at once and then do the glueing. I was exactly where you're at - had the whole system dry-fitted together but knew that, once I started glueing, every dimension would be off. With the help I got above (which of course was confirmed by a neighbors cousin/plumber AFTER I was done!), I was able to complete my installation with minimal problems.

Since you have the entire system dry-fitted, you've proven your concept will work. Take a picture of it so you remember exactly what you did.

For this explanation, I'll call the pieces Fitting1,Fitting2, etc. and the Pipes Pipe1, Pipe2, etc. starting from the first fitting I glued. In other words, the assembly went: Fitting1-Pipe1-Fitting2-Pipe2-Fitting3...

I started with a fitting (Fitting1) that would be FIXED in location (for example, the fitting glued to the existing stack), and glued it in place. Then I re-dry-fitted Pipe1 & Fitting2 to Fitting1 to confirm the location of Fitting2 was still correct. With them dry-fitted, I measured the length of pipe REQUIRED between them IF fully seated (remember, the dry pipe is too short). I then cut this new length of Pipe1 and glued it to Fitting1. I then re-dryfit Fitting 2 on the end of Pipe1. The location was off now because I couldn't dry fit it to where it WILL be once glued. However, I could orient the ANGLE I wanted it to be and mark this angle with a magic marker hash between Pipe1 and Fitting2. Now, using the mark as an angle-guide, I could glue Fitting 2 to Pipe1 fully-seated and oriented properly. Fitting 2 should now be in the proper location and proper angle, with fully seated pipe.

Now repeat the exact procedure using Pipe2 and Fitting 3 and you're on your way.

It's not easy to describe in words but, as I said, I was able to complete my assembly with minimal problems (thanks again Speedball1!).

Good luck,
Brian

Thanks to everybody for your help. I kept reading in a number of articles about “dryfiitng your assembly” and I wondered if somebody was doing something different that I wasn’t aware of to overcome the seating problem.
Again, thanks.
Ed

I discovered I can do a 100% "dry fit" by first applying grease to the sockets and pipe ends.
I used food-grade O-ring grease, but in future I will try vegetable shortening. The parts easily slip together 100% AND they then can be dismantled for accurate cutting (use a tube cutter for clean cuts). Assemble your structure as you go until it's complete and you're satisfied with your perfect results.
You must introduce the additional after-step of cleaning the PVC with a mild soap & water solution and clean rags, but your surfaces will bond just fine even if not a perfect clean up. Glen Lincoln, Boise, Idaho