The Glue
Few
plumbing chores cause as much debate as the proper method for gluing PVC
pipe. Everyone seems to have their own ideas and it's one job that causes a
lot of arguments. The people that sell the cement have one perspective,
usually to avoid lawsuits. The installers will tell you the accepted trade
practice and then do it differently as dictated by the real world.
I've had manufacturers tell me that their cement is so good, it can be glued
underwater with the water turned on immediately. They are always careful to
never make that claim in writing. For this article, I will describe the
method I use.
Since I have been gluing pipe (about 25 years), I've had about 3 fittings
blow apart that I could blame on poor gluing. More often, fittings break
because they have too much strain put on them due to stress caused by sharp
angles.
I've had the experts tell me that if fittings are glued properly, the pipe
will explode before the glue fails. Overall, I've found that to be true.
Before I retired, I sometimes glued pipe that was over 4" in diameter, in
areas where a great deal of damage could be caused if things went wrong. I
really don't have the space to cover those special techniques so for this
article, I will discuss the generic method for gluing pipe that has served
me well over the years.
For the average homeowner
shopping at home depot, that small can of blue glue will usually suffice. If
you're gluing irrigation pipe, this glue has worked well for me.
I prefer to use gray glue for gluing water mains that will have constant
pressure. It comes under various brands and is most often described as being
a gray, medium bodied, medium set glue. Medium set means it won't dry too
quickly, allowing more time for the glue to react with the PVC surface. I've
been told that this glue holds up better over a longer period of time.
The
Primer
I recommend primer,
especially when using gray glue. Some people claim you don't need primer
when using the hotter, blue glues. Why take that chance when primer is so
easy to apply. The primer is used to soften and prepare the PVC pipe by
cleaning and removing paraffin that is left over from the manufacturing
process. Most often, the primer is bright blue in color and is used as an
indicator so you can tell where it has been applied. Many building
inspectors will not pass a job if they can't see blue primer showing past
the glue. I caught one contractor applying grape juice after he had glued
his fittings. Nice try, no cigar.
The Job
The following are the
directions recommended by Weld-On brand cement. Most brands are similar but
check the directions on the can to make sure.
- Cut pipe square and deburr. Clean and
dry joining surfaces
- Check dry fit.. Pipe should push 1/4 to
3/4 way into fitting
- Use a suitable applicator at least 1/2
size of the pipe diameter; for larger sizes use brush or roller.
- Apply primer
- Apply a full even layer of cement on the
pipe equal to the depth of the socket. Coat the fitting socket with a
medium layer. Avoid excess and puddling. If necessary, apply a second
layer on pipe. Cement should fill all gaps.
- On bell end pipe, do not coat beyond
socket depth or allow cement to run beyond bell.
- Assemble while cement is wet. If not
wet, recoat parts before assembly. Insure pipe bottoms into fitting
socket. Twist 1/8 to 1/4 turn; to avoid pushout and allow for initial set,
hold for 30 seconds. Wipe off excess.
- Allow 3 mins. for good handling strength
and 30 mins. cure time up to 150 psi�
