There is nothing scarier than a well you own running dry. Especially if that well is the well that feeds your house with fresh water.
Since that is the scariest, and worst case scenario you have to be careful not to jump to that conclusion when troubleshooting the water system of your house. My well did not in fact run dry, but I have had problems. So lets fix them together.
A fresh water system is composed of several components:
- Well and pump - this is the giant lined hole dug into the ground. Sometimes the well is very deep and sometimes it is shallow.
- Pressure Tank and Pressure switch: Like a pressure Accumulator, not water accumulator.
- The house system: this is the part users interact with.
The pump assembly's job is to pull water from the well and send it to the house. Usually well pumps are submersible units that last a very very long time. (15 to 25 years) The well connects through a check valve to the "control" section of the assembly. The check valve prevents water from pouring back into the well whenever the pump turns off. The pressure tank holds the combination of air and water charged with pressure that lets the water actually flow up pipes. Air and water is used because water by itself cannot be compressed, but using air as an energy battery is possible. When a fixture in the house system opens the pressure races to escape the accumulation tank and drives water through the lines. Simultaneously, as the water and pressure escapes the pressure in the tank is reduced until the monitoring pressure switch is closed restarting the pump and the charging system anew.
For our discussion my system has a few more items to consider. First, my entire system is out in the open because it doesn't actually freeze in my neck of the woods very often. Second I have several acres of land that could be watered if so inclined. Second, when we bought the house we had a lawn, a very very big lawn. I'm going to guess around 15,000 square feet. Maybe larger. There are 8 separate sprinkler zones running this lawn so you can see just how large it is. Finally the thing that spawned this article was: when i went to rehabilitate the lawn i had to start with the watering system and when i fired it up. There just wasnt enough moxi to run it.
Sprinkler systems as i have come to learn are very very thirsty water systems. They make the occasional hose flooding or even the washer in the laundry seem small. For example the rain bird 12 series (there low end models ) at full coverage and 45PSI will consume about 1.96 gallons per minute. So four of these on a line will result in 7.86 gallons per minute. This is not an unreasonable output but I actually have systems that are 6 sprinkler head zones. Resulting in a water consumption of 11.76 Gallons per minute. Now were talking!!
The sprinklers rely on a constant pressure rating to extend the watering range to the same length every time. For example if the water pressure drops the range is shortened from 12 feet to 6 feet and the water consumption is also reduced. This is good for the pressure to recover but bad for the system to ensure proper watering every time. This document from Rainbird is a really good literature on the subject. The problem is that irrigating on a pump system like I have is different than a regular city water system. The water consumption must be balanced to the pump in order to maintain pressure. To get into the nitty gritty read this!
Now that we have a basic understanding of all the factors involved we can start our Sherlock like deductions.
When we moved in there was a green and lush lawn that had been maintained by this sprinkler system. We can therefore make a few educated assumptions.
- The sprinkler system worked at one time. So we can deduce that there was both enough pressure and flow to provide water through the sprinklers.
- The system has not been seriously modified since purchase meaning that factors leading to current situation are damage and degradation.
Now to determine what is damaged we can do some more investigation. If there is a leak that is bleeding off flow and pressure the pump should never stop running. Does the pump continuously run? -- No. We could say that the sprinkler system has become so damaged that it now bleeds off more water than can be replenished easily. We can test this by watching the pressure fall off when we open the sprinkler valves, but it is very unlikely that every single line has been so seriously damaged as to cause this drop off. Additionally when we close the system the pressure should quickly return. The pressure does not quickly return to the system.
Okay that means that we are not leaking pressure and water and the pump and well assembly is most likely the problem. Let us then perform an experiment! By shutting off the water lines running to the sprinkling system and house we are able to check the pump and well assembly. Okay isolate, now bleed off water and pressure. With no house to pose leaks what happens? Does the water pressure return quickly? No. So either the shut-off valves don't work, and the sprinkler valves are leaking, and were losing pressure into a broken system that doesn't cause a continual drain or there is a problem with the well. All things being equal the simpler answer is the simplest.
Well lets check the pressure tank... No leaks and we can drain it and re-establish the proper air bubble in it for charging. Hmmm. That has no effect. Ut-oh!
This leaves the well pump. There are a few possibilities for the well pump. They should last a long time so, there could be a hole in the outlet pipe, which would cause slow filling and pressurization. The hole would cause air to get into the line every time the pump cycled and we haven't seen that really. There is no additional noise when the pump first starts. The impeller on the pump could be worn off which would reduce the efficiency in pressurizing the system. All of these possibilities results in well work which I'm not qualified to do. Call the plumber.