Blueprint reading in modern times

By Fred Bretzke


Forty years ago, Duane Paulson (a blueprint instructor legend) was teaching not-so-talented first-year SAIT students how to print in bold letters. He stressed it so much that to this day I still print in capital letters instead of using cursive writing. I’ve learned over the years that many plumbers really don’t have the best handwriting skills.

Thank goodness for technology. Blueprint reading is transferring into 3-D applications. Computers, emails and texting are making handwriting a thing of the past. However, we still need to read blueprints. Even if they are on a tablet at a construction site, at least we can zoom in to read every detail of an equipment list from a commercial kitchen, or plainly identify a foundation view of a house.

We try to teach blueprint reading in a way that allows apprentices to view flat drawings in an orthographic or isometric way. We commence with the front, side and top views of structures and piping systems. Attempting to view an object in 3-D from a flat blueprint is easier for some students than others. I have always been a 3-D minded fellow, so it was difficult for me to understand why some students just didn’t get it. When looking at single pipe drawings or even spool drawings, I remember the instructor teaching that a smiley face or a frowning face would be a great way to identify the correct direction of a 45º elbow.

It’s funny that after years of learning and then teaching students how to draw an isometric drawing, few of them used those skills in the field. Most plumbers that I came across would draw just a top view of their DWV piping on a piece of cardboard from a rough-in box of ABS fittings. Every now and then I would come across a gifted plumber who could at least draw a perspective drawing of his plumbing layout. This would make the interpretation of his layout so much easier to see if it was to code. Too many apprentices have complained to me that there was not enough blueprint reading in the blueprint courses and too much math. We have now incorporated the blueprint reading into our plumbing theory classes.

In the field there was nothing more useful than having the knowledge to properly read or decipher a blueprint on site. Though at times trying to locate a pressure reducing valve on a down feed water system in a multi-storey building was an almost impossible task. Having accurate blueprints or as builds has been a problem over the years, older buildings can be a challenge to see if everything is where it should be, especially after years of renovating. In today’s construction many large commercial buildings are being digitally-enhanced, including the mechanical, which can be easily updated and altered compared to a blueprint.

A significant problem with commercial construction is the overlaying of sub trades work. In the past we would actually make the blueprint layouts or sections in plastic overlays to see what mechanical or structural part of construction would cause time delay problems. It’s not good enough to just master your particular aspect of the blueprint, one must be able to read the difference from HVAC to plumbing, to electrical, to gas, or even any type of structural you may have to work around. Section plans offer greater details in cutaways of equipment or structure parts of the blueprint, while the equipment list gives details of water, gas, electric, DWV and sizes for custom pieces of equipment. The equipment list is vital for preparing an estimate or ordering equipment for a new building; one must comply with the engineers’ specs.

I would suggest that one of the more challenging aspects of plumbing a new high rise, is the base building part and/or the foundation plan grid lines. The measuring of huge commercial foundation plans to ensure that the underground plumbing is in the right place takes time and skill with blueprint reading. This may all end up being made easier with augmented reality. Can you imagine being able to overlay 3-D piping into a real to-scale foundation plan on site? Digital blueprints will change the world’s construction economy, potentially saving billions of dollars in the construction process.


Residential Applications

Houses, or should I say mechanical systems in custom homes, are getting to be quite complicated. Blueprints are necessary to make sure you get it right. For this example, I will use a basic bungalow blueprint to illustrate how to plumb in the underground. Below is a foundation plan. When looking at this blueprint I would look for the mechanical room and try and run my building drain as straight as possible into that room.

According to the 2015 National Plumbing Code you are allowed to zig zag the building drain 135 degrees ( before you need a cleanout. However, whenever possible, it’s still smart to run it as straight as possible through the house to the mechanical room. When running the main stack in the bathroom you are able to install most of your larger pipes in a typically unfinished (no drywall) room. Most times the developer and homeowner would prefer not to see big ABS plumbing pipes in the home. The trick is to check the blueprint according to code regulations for wet venting to see where you can hide your piping without putting in too many boxed in areas.

As can be seen from the blueprints, this house has two three-piece bathrooms and one four-piece bathroom. Hence most plumbers would look at the print and probably stack vent. However, most new homes are not bungalows and they actually have at least one five-piece bathroom or more. Due to this we are now instructing to utilize residential circuit venting from section of the current code. This method is more efficient than wet venting as you use fewer vents, pipe and labour.

Few plumbers really know residential circuit venting very well, due its lack of use. However, if the blueprint offers that the joists run parallel to the main 3 in.-circuit vented branch it is advisable to circuit vent a five-piece bathroom with only two vents.


Check out how to do a residential circuit vent on youtube: search SAIT Plumbing Residential Circuit and Wet Venting.