PLUMBING DRAINAGE SYSTEM

WhenI think about glass pipe, I imagine a mad scientist in some laboratory surrounded by glass pipe. Or a glass maker creating some cool glass shape with heated glass. How many times will a plumber install glass pipe? Actually, not very often, but it would be cool to install glass pipe at least once and it is in the National Plumbing Code so we should have at least rudimentary knowledge of the requirements. Consider where it might be necessary to use glass pipe. One prime example is in a laboratory due to the use of chemicals, hot liquids and contaminated or non-contaminated liquids. Let’s look at this example first. You are going to need a pipe that can withstand very hot liquids such as 450⁰F or 232⁰C. A pipe that is tough, even if it is glass, a pipe that is corrosion free, and a pipe that allows you to see what substance is inside it. The pipe must have a low expansion rate; even lower than steel so it has good heat shock resistance, and the pipe can be taken apart easily for repairs and maintenance. Modern glass pipe seems to take care of these issues.

Glass pipe is great at handling corrosive wastes, due to its resistance to acids such as sulphuric, hydrochloric, nitric, acetic, and to other materials including chlorinated hydrocarbons, hydrogen peroxide, bromines and brines.

I could talk on and on about glass pipe and its pros and cons in various industries, but what I will expand on is its use for our plumbing shops and training. In the 2020 plumbing code, it lists the requirements for the use of glass pipe and fittings in these sections:

In Division A Part 1 Compliance

1.1.1.1. Application of the code

1.5.1. Referenced Documents

In Division B Section 2.2 Materials and Equipment General Section 2.3 Piping

2.3.2. – Construction and Use of Joints

2.3.2.6. – Mechanical Joints

1) Mechanical joints shall be made with compounded elastomeric rings that are held in compression by a) stainless steel or cast-iron clamps, or b) groove and shoulder type mechanical couplings. There are many code clauses in the 2020 plumbing code for stainless steel pipe, and many similar uses for it in the previously mentioned industries. Stainless steel even has a higher temperature rating of up to 750⁰F. It is also very tough, corrosion free and great for contaminated substances. You could say there is more use for this piping system in dairy systems than the glass pipe that is more prevalent. The only problem is you cannot see through stainless steel. Glass still has some unique uses that stainless steel can’t qualify for. There are even newer forms of plastic pipe used for acid drains, however glass is obviously more see-through. As I am mentioning acid wastes, the 2020 national code reference for acid waste traps is: 2.2.3.1. 2. The trap seal depth on fixtures draining to an acid waste system shall be a minimum of 50 mm.

Testing The Code

All of this brings me back to the subject of plumbing shops and glass pipe. We really wanted to make a piping lab where we could demonstrate the use of vents and traps in a plumbing drainage system.

After designing a 3D example of a glass piping system, we decided to order glass pipe and build it. This then brought us to our next dilemma, which was the cost of glass piping. We were forced to use some of our existing glass piping and fittings and then purchase new transparent plastic pipe for our new lab. This was also expensive, but still one-sixth of the cost of glass piping.

We were almost finished this lab just before COVID hit us. It’s great for teaching anywhere from second- to fourth-year plumbing apprentices. We’ve been able to prove code debates on the use of symmetrical double wyes for horizontal wet venting from 2.5.2.1. This lab is unique as we have installed shutoff valves on all the vents so that we can illustrate trap seal loss from back pressure or lack of venting.

We use this lab for instructing residential circuit venting and wet venting. In 2.5.3.1. 9 b, it explains that all trap arms, including the fixture outlet pipes, must be 2 in. or 3 in. for a 3-in. circuit vented branch. We decided to test this code, and make the bath tub (tied to the CVB) trap arm 1 ½ in. instead of 2 in. minimum. We ran water through the transparent glass and clear plastic piping and watched the glass P-trap to see if the water seal in the trap would go up or down or even fluctuate. There was a tiny bit of movement but hardly any, so what we can derive from this is that our pipe is really oversized.

This information helps us teach the fact that we do want to keep our sizes the same as the tables, which allow for a two foot per second flow. We are usually more concerned with not under sizing the pipe and fittings, but this lab has also taught us not to oversize the pipe.

Another cool thing we have been able to use this glass and transparent piping for is the use of symmetrical double wyes on a horizontal wet vent, just like we use a bungalow fitting or a side outlet tee wye on a vertical wet vent.

We’ve tested this wet venting procedure with gallons of water draining down the lav portion of the wet vent to see if the lower transparent bath tub P-trap would fluctuate or experience some sort of trap loss. Sure enough, the tub trap seal didn’t experience any trap seal loss or even go up or down. This lab has once again proven that a symmetrical double wye installed even on the run of the water closet trap arm works perfectly.

GLASS PIPE & FITTINGS DETAIL

1. Glass pipe comes in many different sizes for DWV (from 1 ¼ in. to 6 in.).

2. Its pressure ranges from 50-75 psi.

3. Its lengths come in 5 to 10 ft.

4. Each length has a glass bead on the end of it.

5. The special MJ couplings come in bead-bead, bead-end, and end-end.

6. The fittings are the same variety as plumbing DWV fittings.

CUTTING AND ASSEMBLY OF GLASS PIPE & FITTINGS

1. Measure the cut.

2. Mark the cut.

3. Score the pipe with special inside cutters.

4. The cutter has a guide that keeps the tool true to the centre of the pipe and a tensioning handle to lock the cutter at the point at which the cut has to be made.

5. Score it by turning the inside cutter a complete single 360⁰ revolution.

6. Heat the pipe with MAP gas.

7. Tap the score mark and your pipe will separate easily.

8. When assembling the pipe, make sure you use the correct MJ coupling, whether it be bead-bead, end-end or bead-end to match the appropriate pipe.

9. Use only a spray bottle of water to lubricate the neoprene part of the MJ, do not use any jelly as it may harm the neoprene inside of the coupling.