Do you dry-fit PVC?

Robert O'Connor_12

Sounds good to me!
Thanks.

Robert O'Connor/NJ

Ken C.

Most of my 4-1/2 years experience has been in service/repair plumbing, but now I’m doing mainly construction and want to get better and faster at running PVC DWV pipe. People I’ve worked for/with are divided on whether or not to dry fit.

Personally, I like to dry fit my PVC before I glue it. No matter how carefully I measure, my measurements always seem to be off when I glue an assembly up. Also, I tend to use the “eyeball” method of piping an offset, instead of using mathematical formulas to calculate offsets (I hate math). A few others I’ve worked with like to dry fit too.

On the other hand, I’ve worked with others who don’t dry fit PVC pipe/fittings. Once they measure, they prime, glue and go on to the next joint. Usually, they’re reasonably close, if not dead-on.

How can I get more accurate measurements and overall, more confident running PVC in new construction?

Al Letellier_8

glueing PVC

The answer to your question is a simple one: practice practice practice....it's just a matter of gaining confidence in your abilities. I've been doing PVC work since it became legal in Maine and I rarely dry fit anything...except for those really tight spots that crop up occasionally....I do use math when necessary but most is eyeball fitting and trust your ability....and your eyeballs. I bet by now you can pitch pipe without a level and can run pipes parallel and even without much effort...training your confidence is a little harder...jsut keep working at it. Strive for quality and mistake free work and the speed will come later.

Robert O'Connor_12

The Lone Wrencher.

If you improve your math skills even a little, this will improve your piping skills as well as your confidence. By knowing exactly what the fitting allowance is, instead of eyeballing it will result in quicker neater jobs. I just finished a job where there was a forty foot ceiling (I hate heights) I prefabed 90% of it out of place as well as installing unistrut in the pour so I didn't have to drill my hangers. Learn your end to center, your center to center and your 45 degree offset. Dry fitting in certain situations will always exist in smaller diameter piping but if your doing new work, you MUST produce or your done.

Robert O'Connor/NJ

bob young

pvc

when running drainage piping we usually dry fit,scribe and mark w/ magic marker some fittings [wye's etc. ] that if glued and needed adjustment for rolls or pitch it would not be possible. as you know with glue it is a one shot deal. better take that extra few minutes than have to scrap a set and start over. that is one benefit of working with cast iron no-hub. adjustment or replacing fittings is no problem.

bob young

pvc

when running drainage piping we usually dry fit,scribe and mark w/ magic marker some fittings [wye's etc. ] that if glued and needed adjustment for rolls or pitch it would not be possible. as you know with glue it is a one shot deal. better take that extra few minutes than have to scrap a set and start over. that is one benefit of working with cast iron no-hub. adjustment or replacing fittings is no problem.

Tony Conner_2

Offset Chart

Here's a chart out of an old Crane catalogue. I know for a fact it works nicely for 45* screwed fittings.

A lot of guys have trouble getting the 'A' dimension on this chart. You need to take two measurements off a common reference, like a wall, floor/ceiling, existing duct or pipe, joist, etc. Imagine the left edge of the page as the wall you're running parallel to, and you need to do a 45* offset. Take one measurement from the wall to the centreline of the pipe or hanger furthest from it. Write that down. Take another measurement from the wall to the centreline of the pipe or hanger closest to the wall. Subtract the smaller number from the larger, and that's the centre to centre distance, or 'B2' on the chart. Now just subtract the fitting allowances (you'll need to determine those, if they're not the same as the dimensions shown on the chart) and cut the pipe to length.

This takes a little practice, but once you get it, it works like a charm and is WAY faster than the trial & error eyeball method. If you've got the tables for the various fittings, this method works for everything - tees, unions, couplings, etc. A lot less scrap, too.

bob young

45 set

if you need to carry crane's chart to figure a 45 degree set you are in the wrong business.

Tony Conner_2

Then...

... I know a LOT of people who are in the wrong biz.

Tony Conner

So You're...

...saying guys like "The Lone Wrencher" should get drummed out of the corps 'cause he doesn't like math? You can actually do things like multiply 26 - 5/8" by 1.414 in your head to figure the centre to centre? Really? Wow, I'm impressed. I have to figure it out longhand with something like a piece of soapstone on the floor, or use a calculator. I consider myself pretty good at math, but the chart is faster - and that's a fact.

Tony Conner

There's Also...

... the "framing square" method for 45* offsets. Determine the 'A' dimension - say for example that it's 12". Lay your tapemeasure diagaonally across the square on the 12" increment on both the blade and tongue. It'll be 17", and that's the centre to centre of the offset piece. Remember to use either the inside OR the outside scale on both sides of the square - don't "mix and match". For bigger offsets, or if you don't have a square handy, you can use anything that makes a 90* angle - top of a tool box, workbench, corner of a room, etc.

bob young

\" box \"

the " box " or framing square is a time tested true pipefitting method which will not fail you.

bob_50

The Lone Wrencher

If you are serious learn the math, I recommend Pipefitter's Math Guide by Johnny E. Hamilton. You could do like a lot of plumbers and just buy a Lufkin plumbers rule or to take tony's example take the A demension one and onehalf times and subtract 1/16" for each whole number. You don't even have to take your pencil out of your pocket. Put your thumb on your rule at 12" now run it down to 11/2 times to 18" slide it back 18 1/16ths to 16&7/8". Tony's answer was a 1/32" long. Not dead nuts but close enough for plumbing. This is more of a visual than a mental process, I think the Romans invented it because of the brain damage caused by working with lead or plumbum. bob

Robert O'Connor_12

\"The Box\" and The Lone Wrencher

The simple way to figure your "box" in relation to laying out a 45 (or wye)is to obviously know where your main is in relation to your center. If the main is 12" off the wall (center)and the center of your stub up is say 36" off the same wall (or 2' center to center) you need to find out how far the 36" measurement is off the other wall (up stream). Say the 36" number is 5' off the other wall and YOU need to know where the center of your wye is going to be (down stream obviously), simply mark 5' off that far wall (where your main is) then add 2' to it because your center to center is 2'. If its 2' c to c then the distance back to the wye shall also be 2'(from the 5' mark). Framing squares are for framers (or a welder) everything else can be figured with simple math and I mean simple. If you can't do 1.41 (for plumbers this is the most common) ya better learn for thats first year apprentice stuff.

If you need help or you need trade math guides let me know I'm sure I have a few ol'"Starbuck" books collecting dust. I'm sure Bob Young has the same one(s) too. I have a very small pocket size chart for ALL offsets as well as rack measuring guides I just don't have a scanner. If you are REALLY interested I'll see if I can get my hands on one for you........Whew!


Robert O'Connor/NJ

grindog

fat max

stanley makes a good tape measure for plumbers who like to eyeball there offsetts. comes in handy when your holding a 4" service weight wye over your head.

bob young

proper pipefitting techniques

now we are actually making some progress. bravo Robert O'Connor & Tony. great advice all.

Robert O'Connor_12

Thanks Bob but...

What ever happened to the lone wrencher??


Robert O'Connor/NJ

bob young

Probably down at home depot buying a lufkin folding rule & a framing square. or got a job at mc donalds [ no math necessary ]

Dave Yates (PAH)

Wow!

Everytime I see a work of art like that, I can't help but wonder about the amazing attention to detail and artistry that went into its creation and how many hours must have been expended to create the tool. It's obvious they took great pride in their work and wanted the appearance to be as functional as the chart. I'd be proud to carry something like that with me. Thanks for the link!

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Robert O'Connor_12

I had one of those rulers

Years ago I had the offset ruler. The only problem was I accidentally used it to fab up something ELSE!! ARGH!

Robert O'Connor/NJ

hr

Some PVC thoughts

Often times the pipe will not go all the way into the fitting until the glue (lube) is applied. If you do a bunch of dry fits is a row this could add up to a problem.

Invest in a PVC wheel for your large tubing cutter. I hate watching a hack, hand saw a piece of pipe with a 11 degree angle to it. It never goes into the fitting accuratly. A nice cutter with a sharp plastic wheel is just as fast and more professional.

Or a PVC chop saw

Get a fan to blow those nasty PVC glue fumes away from your work area.

It's good to know how much run the various fittings take in a system, especially when working in shallow joist bays. This will come to you with time.

Use the "force" I mean math, young skywalker. It's worth the time to learn the formulas for fitting. Some master plumbing test still require you show the math when doing your fitting on the pratical portion of the exams.

hot rod

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Rookie

PVC work

Good advice from Hot Rod about the PVC cement and solvent, get a rated mask for organic chemicals and use it, always have a ventilated area you are working in, never compromise your health for a lousy new house rough. If you don't have one buy a chop saw, and bevel the edges of your pipe, and clean the burrs of the inside of the pipe. If your a real poke on the roughs you better get help soon, get to the job early and stay late, do drawings at home, go to roughs that your other co workers are doing, another suggestion is if you ( some companies frown on moonlighting)can moonlight with some other plumber that is good, even if you have to work cheap learn his secrets, most likely no one at your company will take the time to teach you, because your all in competition ( when your on the new construction crew)so you better learn to hustle. But, on the other hand if your a good service plumber you will always be a commodity.Good luck.

Boiler Guy_2

Offsets

I do not engage in much "fitting" anymore myself but it aggravates me to no end watching a lot of "newbies" in the pipe fitting trade cut 10 pieces of pipe to make a simple 45* offset. I learned from some of the best to make it right the first time many years ago. If my memory serves me correctly my first sprinkler foreman had a coated card of the same page posted here. Excellent trip down memory lane. Thanks

Tony Conner_2

But...

... plain old framing squares are shown for figuring piping offsets in both the "Pipe Fitter's And Pipe Welder's Handbook" & the "Pipe Trades Pocket Manual" by Frankland, and "Pipe Trades Handbook" by Lee. The "Pipe Fitter's Handbook" by Grinnell and the "Pipe Fitters Manual" by Tube-Turn both show a lot of welded pipe fitting methods with a framing square.

For anybody interested, Mathey Dearman makes a square specifically for fitters, called the ... wait for it... pipefitter's square. Most guys on this board would likely never use it enough to make it worthwhile on the job, but it IS a pretty cool tool

http://www.mathey.com/documents/PipefitterSqManual.pdf

Kal Row

make fun all you want...

but by eyeball, you would never be able to create works of art like the dead men who did those amazing gravity feed hydronic systems - i stand in awe whenever i come across one

Bob Sweet

Not everyonews cut out to be Di'Vinci

I say help a guy out, dont castrate the Man for asking a SIMPLE question.

mp1969

Dry Fit?

Robert O'Connor_12

Bob Sweet

Who castrated him? It appears to me like he got some good advice. Lets face it, not everyone receives the same education, thats why we have apprenticeship programs. The problem I see today is that anyone with a hack saw and a can of glue hangs up a shingle and calls themselves a plumber. Installation of house plumbing today (new work) is a joke, builders could care less about the qualifications of their subs (or the quality for that matter)as long as they produce. Most of the larger house plumbers (new work) today acually sub out the rough work to inexperienced hacks for which the greater majority are not licenced not bonded and not even insured and perform their duties as piece work. Giving someone $75 to rough out (per fixture) and then only paying them IF the job passes inspection in my opinion is down right wrong. If you want to bring new people into this trade today, somethings must change. By mandating that ALL employees working at the trade MUST be either trained as in a formal apprenticship or received matching credentials from a trade school will be the only way to provide a "living wage". The poster claimed to be at it for quite some time although doing service which really isn't the same thing he still should have received some sort of an education or reference material that he could pull from. I personally think the advice was sound and that ANY first year apprentice worth his salt should know 1.41.

Robert O'Connor/NJ

mp1969

Dry Fit Everything?

After 37 years in the trade I am surprised that so many professionals do not have common offset multipliers in there heads! The DIY centers recommend dry fitting at their Saturday seminars but let's be real!
Apprenticeship courses in the four states I have worked in all teach piping installation and measurement during the early years of there programs.The rule of thumb is accuracy before speed but housing plumbers are all about speed (once they master the accuracy)
We use a cutoff saw for 3&4" and scissor cutters for 1- 1/2 and 2" (bevel outside edge with the cutoff saw and jacknife the burrs off the inside edge.)
Dry fitting under gound piping is unheard of and makes little or no sense due to the dirt and debris that can get into the joints.
I have never had a job rejected and our firm is known for it's quality workmanship!
Come to Wisconsin for two weeks and I will personally train you how to roughin a house by starting with the abovegrade DWV and fitting up to it with the belowgrade soil stacks and waste stacks.We could use three more mechanics for service so we will keep you busy with fill in service work while you quickly learn piping techniques.
Cost effective plumbing firms have to master this aspect of the trade (no exceptions)
Good luck but I am sure that if you have been a quality service plumber you can easily pick up piping techniques without dry fitting everything ( we only dry fit when there are close offset connections with tight space restrictions) 1.414 is not hard to remember (the multiplier for 45 degree offsets) in fact, that was part of our practical test back in 1974 when I took my journeymen's exam.
One of the disadvantages of service work is that apprentices are put into the service trucks before their apprenticeships are complete(due to cost effectiveness once again) Conventional apprenticeships with a journeyman teaching and inspecting all the apprentice's work are rapidly becoming a thing of the past.

Need any pointer's I am at: rkontny@charter.net

Bob Sweet

Dont get me wrong Robert

"if you need to carry crane's chart to figure a 45 degree set you are in the wrong business" say's it all.

A little tact goes a long way.

Have a nice day.

circa on that chart 1932

Jimmy Gillies

1.414 Multiplier

Thanks for the multiplier for a 45* offset, do you know what it is for 67.5*/22.5*, a common rainwater pipe offset angle here in the UK.
Where's Pythagoras when you need him!!
Regards.
Jimmy Gillies (Scotland)

bob young

serious pipefitting

after reveiwing the mathey dearman spec. sheets the lone wrencher might have a slight coronary ,Tony. they do get very deep !

Robert O'Connor_12

Mathey

I got two mathey ez-clamps and they work great. I have had the pleasure to work with several other large diameter jigs as well. Mathey is a bit pricey but his products are well worth it. The square does have some great shortcuts. I would highly recommend it.

Robert O'Connor/NJ

Mark Hunt

Robert


Some day I will buy you a drink.

There is more to this trade than "stuff" running down hill.

Kudos sir.

Mark H

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bob young

offset constants

the constant a 22 1/2 * is 2.613 & a 60 * is 1.155 never heard of a 67 1/2 * fitting but you could figure it out with square root if you wish or call up the chivas regal people. they would know the answer

FRANK_24

My two cents worth is: on certain joints I like to use the gray cement. It's a slower setting glue and gives the plumber a few more seconds to align the joint

FRANK_24

I've been in the P&H trade over 35 years and always used the eyeball method, using a few try pieces in the fittings, lineing up the offset, and needing someone else to take the measurement when using larger pipe. Most of the time it worked out fine. Sometimes not. Wish I knew about this chart. I've copied it, laminated it, and giving it to all the P&H gang. It's a good tool. Thanks for the link.

Kal Row

about 45's, i must be missing something...

i simply set up the straight runs first, then messure the distance of the 45 side from inside stop to inside stop, then cut'n'paste - works perfect, so what's the problem???

mp1969

Shagging

We would call that shagging Kal, a line of site method that can work but has it's limitations. I went through my apprenticeship from 1969-1974 when we still used galvanized waste and vent system, you had to be very precise and retreading or recutting was a quick way to be demoted to putting in hangers and digging!
Call me old fashioned or old schooled but shagging is not a good way to install piping!

Kal Row

\"Shagging\", not to be confused with \"laying pipe\" ...

i dont recall having to reCut or reThread - only dismounting one end, to assemble