Technique for dry fitting PVC pipe?

[trader4]

In previous projects I really haven't had the need to dry assemble a bunch of fittings to get the alignment right and make sure it would all work before gluing. In the case of some recent work with 2" PVC I had pipes making a tight 180 turn and together with a 3 way valve, it all has to align just right with the existing piping in a short distance with no wiggle room.

So, I put the pipes and fittings together dry first, to make sure they aligned OK. But there were two problems:

1 - It was very hard to get the dry pipe to bottom in the sockets of the fittings

2 - It was even harder to then pull them apart.

I tried using some dish washing soap, but it didn't help much. Which got me to wondering if there are any tricks the pros use?

[The Post Quartermaster]

Seems I remember someone long ago saying they used talcum powder. I'd try just one joint first though.

[jamesgangnc]

I have the same trouble. I do a little at a time rather than trying to dry fit an entire line. Sometimes I make some marks on nearby things as to where turns and valves and such have to end up.

[Joe]

Newer PVC seems to have more of the tight fit problem than I can recall from past projects. Nowadays I routinely use regular machine shop type sanding strips to get a decent moveable fit. With the heavily bodied cements (resin containing) being used it should make no difference at all in mechanical integrity. Haven't had any leakers, ever, in doing this. Using sanding strips makes it less likely to make a dumb mistake such as making a groove with a flat file that could leak.

Joe

[dpb]

[e-mail] wrote: ...

The biggest "trick" I think the pro has is the experience and practice such that can make stuff fit properly simply by measuring lengths minimizing the need for nearly as much dry fitting as we diy'ers.

My general approach to a similar situation tends to be to do one joint at a time so to minimize the accumulated measurements required and then the last assembly generally isn't bad. Any given situation can lead to peculiar issues, of course that might make more trials a useful exercise.

$0.02, etc., ...

[trader4]

The problem with one joint at a time is that if an earlier joint has a freedom of movement that affects the positioning of a fitting that is coming 3 connections later, if it it gets set at the wrong angle you then can't make the last connection. Which is why I needed to dry fit several fittings and short lengths of pipe simultaneously.

[RicodJour]

Ain't those situations fun? I've had to create some new swear words - like Ralphie's dad in A Christmas Story. I use a Sharpie to make some alignment marks on each joint, and then glue pieces up into assemblies and then glue up assemblies. I don't know how critical it is to have the joint bottomed out. Preferable? Sure, but I don't think it affects things too much. When I've cut into other people's work I've found substantial gaps where the pipe didn't bottom out in the fitting, but that didn't seem to create any problems with drainage.

R

[DD_BobK]

PVC pipe / fittings are not meant to completely dry fit to the same depth as when doing the final glue up.

On the solvent glue cans, the instructions often note that dry fitting should result in insertions 1/2 to 1/3 less than full depth.

The solvent action of the glue allows the pipe and the fitting to "mush" together.

but back to your original question....

The fittings are not meant to be dry fit completely. If you need to get things to fit up exactly correctly, sequence your assembly and measure the socket depths. Using primer & glue you should be able to get the pipes to completely bottom.

Marking pipes & fittings so that desired orientation is maintained can be helpful.

cheers Bob

[Larry Fishel]

His concern was that if he carefully measures and dry-fits everything, then when he applies the solvent the lengths will change and the assembly will be FUBAR.

[don &/or Lucille]

[RicodJour]

The alignment marks have markings for rotation angle and depth, at least that's the way I do it.

R

[Doug Miller]

That's why you should carefully measure and *not* attempt to dry-fit. Measure to the bottom of the seat in each fitting, because that's where the pipe is going to wind up when the solvent is applied and the joint is made properly. Trying to dry-fit plastic pipe is an exercise in futility: the pipes *never* bottom in the fittings, so there's no way that the final assembly (with solvent, and hence with the pipes bottomed) will be the same size as the dry-fit size.

[Doug Miller]

Uhhh.... no. No. NO!

Please don't attempt to give advice on subjects you know nothing about. The primer/cleaner makes the pipe sticky, not slippery. No way will it work as a lubricant. Good grief.

Please don't top-post, either.

[aemeijers]

Deburr (and maybe even chamfer like a dowel) the hell out of square-cut ends, is the one plumbers always told me. The 'slip fit' for new pipe and new couplings is pretty tight anyway. One burr or non-square end cut can make the dry-fit a case of pounding an oval peg into a round hole, if the approach angle is slightly off 90 degrees. Even more so when you are using glue with a very short open time. This is why ground assembly, and making as absolutely few joints in the air as possible, is the best approach for DIYs. My BIL did some feeds, drains and vents for his washing machine move that look like something out of Rube Goldberg, to get all the runs to line up. Too bad about the stud and plate that used to be there. He would have been better off cutting the whole mess back about 15 feet, and starting over. (What can I say- he is a college professor with a green thumb, and a nice guy, but he is no DIY. But my SWMBO sister will not be denied.)

[trader4]

You can easily measure lengths in most cases. But when you have a complex series of fittings at angles within a small area that has to then align with 3 existing fixed pipes, it's not just a matter of simple measurement. You need to know the angles can come together correctly together with the various pipe lengths involved.

[trader4]

Yeah, I kind of thought about that. I guess you could use a Dremel or similar and grind it out. Would be cool if they sold alignment ones that were slightly over sized and a different color, like red, so they wouldn't get used improperly.

[Evan]

Umm... yeah... If you have that sort of problem and need to dry fit because you can't measure the lengths needed and visualize the angles, you are probably lacking enough skills so that you should hire someone to do the work for you even though you know how to glue the pipes together yourself...

~~ Evan

[trader4]

Explain exactly how one "visualizes" the angles. Seems everyone else here understands the issue, because like me they have had cases where it is necessary to dry fit prior to assembly. In the case in point, I had a 3 way 2" valve that had to align with 3 different pipes on 3 different levels, all within a tight area. This isn't a case of running a waste line across a basement, where the angles and lengths aren't critical, you can make it up as you go and make adjustments farther along if needed.

[workman.larry]

The process of dry fitting, PVC pipe(s) and fitting(s) is fraught with prob lems. This is because the industry standards for both the pipe and the fit ting socket are designed to provide an interference fit within the bottom 1 /3 of the socket. This is where the solvent in the cement creates a fusion bond of the pipe and fitting. The socket of the fittings have a slight ta per, to assist in rounding the pipe and achieve the fusion bond area necess ary to provide a leak free, joint that can withstand the forces of the sys tem pressure. Sanding or grinding the diameter of either the pipe or fitting can jeopardi ze the quality and/or performance of the solvent welded joint. Pipe fitters that fabricate pipe assemblies use the takeout dimensions prov ided by ASTM standards for PVC fittings. These dimensions can be found wit hin ASTM D2467. Another choice for getting the takeout for PVC fittings ca n be found at:

There are two FREE options that can provide you the takeout you are seeking. First is the html page at: htt p://expert4pvc.com/HandyTools.html or the Android app at: http://expert4pvc .com/Android.html

[trader_4]

oblems. This is because the industry standards for both the pipe and the f itting socket are designed to provide an interference fit within the bottom 1/3 of the socket. This is where the solvent in the cement creates a fusi on bond of the pipe and fitting. The socket of the fittings have a slight taper, to assist in rounding the pipe and achieve the fusion bond area nece ssary to provide a leak free, joint that can withstand the forces of the s ystem pressure.

dize the quality and/or performance of the solvent welded joint.

The idea was to grind the necessary ones out and keep them for fitting purp oses. When actually assembling, you use a normal one. They only cost $.50.