Pressure Tanks

You could be stepping in it, literally, if you mess with a sight glass on a pressure tank like columnist John Schmitt did. Source: iStock

In my first article on this subject, I talked about sizes of tanks, why they are needed in a hydropnuematic system and a variety of tappings that we don’t see in modern tanks.

One thing that was quite common back in the day and that we don’t see at all anymore, at least in smaller tanks, is a sight glass. This was a small glass hollow tube that ran up the side of the tank. They were usually installed about two-thirds of the way from the bottom to the top. The tanks would have tappings, usually -inch IPS, where special fittings that accepted the sight glass could be installed. As I remember, these tappings were about 18 to 24 inches apart. The glass itself was maybe -inch outside diameter, and it was protected on the outside by two brass rods so it couldn’t easily be broken by being bumped.

I believe the purpose of the sight glass was so that the operator could see the water level in the tank and determine the air-water ratio. In those days I think the “best” ratio was somewhere between 25 percent air under pressure and 75 percent water. Sometimes, this was as low as 50-50 and my dad always liked one-third air and two-thirds water. In any event, the sight glass gave the pump man or the owner an indication of the air-water ratio — that is, if everything worked properly. As I mentioned in my first article, the mineralization of water in Michigan, while in solution and invisible straight from the well, rather quickly became in suspension in the pressure tank and coated the sight glass, making it useless.

As I remember back, it seems to me the special fittings that the sight glass was installed in had valves on them. I believe the idea was one could close the valves and change the glass or clean it without draining the tank. In hindsight, the smart thing to do would have been to keep the valve closed at all times except when servicing the system and the sight glasses would have remained much cleaner. I don’t ever remember finding any of these valves closed. I believe this would have worked just fine, as I used it on a bypass system on the flow meter of a geothermal heat pump that I had in my house for over 22 years. When the unit finally failed, having given long and valued service, the meter was as clean as the day it was installed. And, yes, I have the iron-laden, mineralized water that is common to southern Michigan. Incidentally, a good iron filter followed by an equally good water softener puts an end to the nasty mineralization for our domestic use. If you have water like I do and install a system like this, it will make your wife extra happy.

This sight glass system became the basis for a mini-disaster in my career. One of our customers was a small community of about 12 homes whose water supply was a single 6-inch well with a small-line shaft turbine pump connected to a 1,500-gallon tank buried into a hillside. One end of the tank stuck out into a well house and the well itself was inside that house. The contractor that installed this system had passed on and some years later we were contracted to replace the pump, which we changed to a submersible. This system served 12 single-family residences and the water was supplied, I found out later in doing some repairs, with a combination of cast iron water main, steel pipe, some early large diameter polyethylene and copper tubing from the main into individual houses.

Some years after we replaced the original pump the State Health Department, which regulated this system as a community system and rightly so, said that they would have to have a second well as a backup. Now this makes good sense, as no matter how big a well an owner has and a pump to match it, if something goes wrong the user or owner is, as I said in my last column out of water — or OOW. Now, this little community even had a water board made up of three of the residents. We met with them and came to an agreement to drill a new well outside the well house and equip that well with a pitless adapter, which was unheard of when the original well was drilled, and a pump identical to the one in the well house.

The drilling went without problem and we got a good producing well, installed the pitless adapter, and submersible pump, and ran a line into the well house where we connected it to the 1,500-gallon tank. As we were finishing up our installation, I noticed that the sight glass was all rusted and of no use. I told my dad we should clean that glass and he replied that it can’t be done. Determined to show the old guy that his less experienced son knew what he was doing, I took the sight glass system apart (closing the small valves before I dismantled it) cleaned the glass and put it back together. My dad said that when you put pressure on it the glass will break. I put the pressure on it and the glass did not break — so much for what my dad thought he knew. Unfortunately for me, he really did know.

About a week after we completed the installation, my mother drove out to a job where we were drilling and said the water board for this community had called and had real trouble. We quickly shut our rig down and drove directly to this job where we could not help noticing water gushing out from under the well house door in a not so small waterfall. Guess what? My dad knew what he was talking about after all — the sight glass had indeed broken. Wearing high rubber books I waded into the well house, closed the valves on the sight-glass fittings and we ordered a new sight glass that we installed. It worked just fine and held up, too. Fortunately, no real damage was done since the well house had a concrete floor and sides, and the well inside terminated above the level of the door threshold. I never have figured out why these glasses will fail when taken out and then put back in. I think it has something to do with stresses on the glass. It was a very embarrassing incident for me.

In my monthly weather report, as of mid-May as this is written I have actually mowed lawn twice and a week ago we had a hot, humid, ugly day typical of Michigan in the summer. Then a front went through and it was in the mid-30s for several mornings and we had frost on the deck of our house. ‘Til next time, work hard, work safely and be darn careful around those sight glasses. 

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