Let Me Tell Ya: More about Drop Pipe
Last month, I wrote about galvanized steel pipe as drop pipe for several types of pumps, and some of the problems associated with this material. I realize that galvanized pipe still is used in many areas, certainly on larger submersibles, and while it has some problems, in certain conditions, it is a good material.
In the years right after World War II, the jet pump became far and away the favorite-type pump used here in Michigan. It was a much simpler system than the stroke pumps we had used in deeper settings, and the submersible was in its infancy and not very popular at all. A new-and-improved solution to drop pipe used with jet pumps, at least those of the two-pipe design, was to use the newly introduced plastic pipe, which was a black-colored polyethylene material. This plastic pipe seemed like a godsend, as it uncoiled like a garden hose, could easily be cut to any length, and did not require threading, as it used so-called slip-type fittings held tight with a clamp. The fittings were necessary then, as now, to get back to IPS, or iron pipe-size threaded joints to connect to the pump proper and ejector bodies.
Polyethylene plastic had the additional benefit of being much lighter in weight than black or galvanized steel, and one could make up an entire length needed for a system and just slide it into the well casing. Perfection in itself – well, maybe not quite.
After a few years of use, the shortcomings of this type of pipe started to become apparent. The first of these was that this early poly-pipe didn’t have a real high working pressure. If I recall correctly, we installed a lot of 80-psi-rated pipe and maybe some that was rated at 60 psi. This was fine, as we were, after all, running 40 psi maximum on our system. What we installers failed to realize was as the pipe went down in the well, every foot above the water line gave us added pressure, and sometimes this was enough additional pressure to cause the pipe to fail. Looking back, I think perhaps the manufacturing methods of those days weren’t as good as we have today. In any event, we started to experience splits in the poly-pipe, and it had to be pulled up and repaired. This brought to our attention another drawback – the pipe had to pulled by hand. Now, unlike installation, where we had dry pipe, many times the pipe or pipes were full of water, as the splits were small enough that the pipe was not self-draining. Unlike steel pipe, this poly-pipe did not lend itself to a mechanical means of lifting. So we had to “horse” it out of the well, and it could get darn heavy. On top of that, below the water line, the pipe sometimes would be covered with a light coating of rust, which almost seemed slimy. One really had to get a grip, or the whole assembly would slip back into the well. I realize today we have plastic pipe-lifting systems, which usually are some sort of a large-diameter drum that rotates under power. I do not have one of these, but I can see how that would make pulling poly-pipe from a well much, much easier.
One manufacturer – there may have been more – made a really handy dual-type pipe that was one part 11⁄4 inch and another 1 inch, and they were connected together with a light web. This pipe was real handy to use, as both sections of pipe were tied together, and it went into and came out of the well like one big piece of pipe. Unfortunately, this design really was prone to splitting, and we only used this type a few times, and swore off of it for good. I don’t think this type of dual pipe is made anymore.
Another problem that soon became apparent was that the slip fittings we used pretty much all were galvanized steel, and these were subject to corrosion and incrustation, just like steel pipe itself. In later years, including to today, manufacturers began to provide these fittings made of brass or stainless steel, and that was the solution to fitting problems. I, for one, have pulled many jet systems, only to find a pin hole or holes near the jet body, just like the corrosion that occurred with submersibles that I mentioned in my last column. There were nonmetallic slip fittings available, and while some of these left something to be desired, they did solve the problem of corrosion.
Another problem that occurred was failure of the clamps that tightened the poly-pipe to the adapter. Some of these were carbon steel, while others were stainless steel bands with carbon steel screws to hold them tight; these both could fail under tough conditions. Manufacturers eventually made available completely stainless steel clamps, and this is the type I have used for many, many years; they have solved the clamp failure problem. A lot of this poly-pipe was used in trenches for water distribution, and where the well was offset from the pump location. When burying poly-pipe in a trench, you wanted to make darn sure you had good slip fittings and the best-quality clamps, as failure would result in a nasty dig-up job.
The combination of poor pressure capabilities and fitting failure finally caused our company to quit using poly-pipe for drop pipe on jet pumps. We went back to either galvanized steel or, strange as it may seem, copper tubing. I will write about this use in a future column. In the late 1950s, manufacturers developed what then was called high-molecular weight or high-density polyethylene. This was available in pipe rated at 100 psi, 120 psi and 160 psi. This, along with improved slip fittings and all stainless clamps, pretty much solved the problems of using polyethylene for drop pipe, and my company went back to using it. We also used thousands and thousands of feet for water distribution lines. Like any process, it took a while to get all the bugs out, but today, polyethylene or PE pipe, as it is sometimes called, is an excellent product that rarely fails.
Many installers in my area now hang submersibles on 160-psi-rated poly-pipe, and it seems to work very well. With the exception of the reel-type lifter, we still haven’t solved the lifting problem. I even have heard of single-pipe jet installations in 2-inch and 3-inch wells using polyethylene as the drop pipe. I never have done this, but if the well produced mineral-free water, I can see how it would work. Next time, I will relate how we used copper tubing as drop pipe, and finally got to PVC material, which is very, very popular in this area today.
As I am writing this in very late November, I am getting ready to leave the day after tomorrow for Las Vegas and NGWA Expo. I hope that by the time you read this, I have seen many of you there, and we will have had a chance to visit. Today, as this is written, it is rainy and dreary in southern Michigan; the grass finally has stopped growing and has kind of a yellowish-green look to it. We have yet to have any snow that lasted more than a few minutes, but we know for sure it is coming. Hope you have had a good 2011, and that 2012 is the best yet.
For more John Schmitt columns, visit www.nationaldriller.com/schmitt.