Completing a job quickly is every contractor's dream. In my 25 years as a Master Plumber, I've learned four key elements to doing better, faster work. Using the right tools, developing a focused crew, and hiring GCs who are good to work with are three things that have improved my work flow. The fourth – and main – ingredient in winning jobs and achieving greater business success is seeking an answer to one persistent question: How can I do this better?

One of my favorite answers to this question is our in-shop rough-in procedure for pre-fabricating both our under-slab PVC rough-ins, and our in-house assemblies like shower diverters and lav risers. The benefits to working in our shop are terrific: weather is removed from the equation, all of our pieces and parts are right there, which streamlines our efforts, we can use parts that would otherwise be wasted on site, and apprentices can do a lot of the work, freeing experienced mechanics for the trickier stuff.

Under-Slab Layout and Assembly. In an empty garage bay at the shop, we snap a crosshairs of square lines then seal them with lacquer to use as control points for laying out our plumbing groups. Off one axis we pop 14-1/4- and 15-1/4-inch parallel lines, which represent the centers of 2x4 and 2x6 walls for toilet layout – the fixture around which we then layout the rest of a bathroom group. The lines are reference points that enable us to snap or draw wall lines of the current job, which we get from the plans, and allow us to pre-fab entire bathroom groups in one shot.

Snapping a grid on the shop floor represents wall-centers, which we use o layout and pre-fab different assemblies.

A torpedo level, framing square and shims guarantee we maintain pitch and plumb and that our fittings are level.

Next, we use a framing square off of our floor lines to project and measure a vertical axis. The lines on the floor represent the centers of our walls, then we line up fittings for accurate measurements and alignment. A torpedo level ensures that elbows will not be skewed as they leave the slab. To keep things perfectly plumb and to grade, a bucket of shims helps us hold everything in position while we glue.

We mainly fabricate the bathroom groups and the building drain using this process, including all branch wyes and second floor stacks. Individual remote fixtures like a kitchen sink or wet bar sink are easier to pipe on site.

In-House Assemblies. Tub and shower valves are also easy to prefab in the shop; so are sinks, lavs, water closet risers, and clothes washer boxes with the valves already installed. You already know valve heights from the plans as well as spout heights and head heights. While weather isn't usually a problem at this stage of the process, other trades can be, so building in the shop almost eliminates overlaps with HVAC techs or electricians and keeps us moving. We even install the test nipple for the shower arm.

Delivery and On-Site Install. If the final assemblies are too big to fit in the trucks, we use a flat bed trailer, otherwise, we truck them to the site in vans. Once on site, we locate a main plumbing wall with a string and "plant" our assembly. With a field verification of the stacks (PVC & ABC do have flex), rough-in is done, and we can cut our labor time by more than half.

John Myrtle is a Master Plumber and technical education teacher in Hotchkiss, Colo.