Most people don't really know how well pumps work, it also turns out that many that should, only have limited understanding. They tend to be limited to what they need, for example, a well installer knows what is needed to make the install, but commonly falls short on important things to know to ensure the pump is long lived.
We moved into a lot with a pre-existing well. A five horse well pump that was submersed is all we knew. It had two pressure tanks on the side and a work bench full of pressure valves and sundry irrigation parts.
I found it surprising that there were so many pressure valves -- all used. The two pressure tanks made different sounds when you knocked on them, one deeper and one lighter.
Now I don't know what you know about the above mentioned, so I'll give you enough to be able to follow along and understand the problems and solutions that I implemented.
There are two main types of well pumps, one is above ground and the other is submersed. An above ground pump is sucking water while the submersed is pushing water, to the surface.
The above ground pump is limited to a depth of roughly 25 feet. Deeper than that and the water is too heavy.
A submersed pump can push water from almost any depth and is more limited to your budget. The height that a specific pump is able to lift water is called headroom or head. The next number is what volume of water per amount of time, for example, 25 gallons per minute. It will have a horsepower rating as well, this will determine the amount of electric power needed. Most submersibles are using 220/240V.
The way this design is supposed to work is that you open a faucet and water immediately flows out of it. For this to work without a delay there must be a pressure pushing water to the faucet at all times.
This is solved by using a pressure tank. It is using air to squeeze water out of the tank. There are two different types of pressure tanks. The older is called bladder and is like a balloon. The bladder is placed inside an air tight container. The air around the bladder is pressurized. Water can flow in and out of the bladder via a pipe that it is connected to.
The higher the pressure the faster water will be pushed out.
The newer kind is called a diaphragm tank. It was designed to avoid the main reason of failure in bladder tanks, namely the large amount of expansion and contraction that it goes through. This results in cracks in the bladder folds over time. The diaphragm is not flexing as much and doesn't develop folds to crack along and so lasts much longer.
You can see examples here: https://plumbingsniper.com/wp-content/uploads/2021/05/types-of-pressure-tanks.jpg
OK, so we have water being delivered under pressure to the faucet. However we still need to turn the pump on and off, this requires a sensor that can tell when the water is running low in the pressure tank. Actually we use the volume of pressure to regulate the pump.
A small device called a pressure valve does this job. It has two adjustable screws to set when it turns on and when it turns off. Commonly it comes on at 38 psi and goes off at 20 psi higher. These numbers can vary with each install.
That is the basic configuration. You have a pressure tank to keep water waiting at each faucet, and a pressure valve to refill the tank. This is all good but not enough to keep your pump running for many many years.
The reason we had a bunch of used pressure valves from the previous owner(s) was that the valves had, at least when we moved in, no information on them to indicate their specifications. We are talking about the amount of power that they are able to reliably break (turn off). Thr power is what the pump is drawing, and is usually around 6-10kW. That is a fair amount of power. If the switch is not made to break that amount of power, it will burn out.
All the pressure switches I had on that workbench were burned out.
Looking over the device for the specifications it was designed for revealed -- nothing!
I had to do a deep dive into the manufacturer's website and data sheets to see they were made to handle up to 2.2 HP.
My pump was a five horse power pump. Clearly outside the specs of the switch! No wonder they burned out.
OK, when I went looking at my local big box store, none of them listed the specs.
During this time I had a working pump which was delivering water. And then it stopped running, the switch was worn out and I was simply replacing it with another one.
Having learned about the specs, I was able to come up with a solution which removes the problem all together. The standard answer when you need to break more power than the switch is able to, is to use a relay. A relay is able to break a larger amount of power than the switch.
In my case I chose a relay able to break 100A at 240V (24,000W). At least three times stronger than the load it had to deal with, meaning a lot of margin. The relay draws 1A 110V (110W), which means the load on the pressure switch is now negligible and it will not burn out.
As we moved forward, the 5HP pump burned out. While researching new pumps I learned that there is another pitfall: namely overheating the submersed well pump. Turns out pumps up to 2HP need a minimum of 1 minute of run time to cool down, while larger pumps need 2 minutes.
My tanks were being refilled in around 30 seconds. So, too little time to cool
Those pumps can run for months nonstop, but not less than those minimums.
So I set out to learn about the pressure tanks and discovered that the one that made a deep sound did so because water had filled the whole container, meaning the bladder was leaking. Our tanks had a total of 80 gallons capacity, of which 22 gal were water, the rest is for air.
Calculating how many pressure tanks we would need I discovered that the newer diaphragm tanks are much smaller at maybe half the size, but hold twice the capacity of the older kind. The well house was not large enough to readily hold enough of even the newer tanks, in enough volume to increase the run time. Then there was the issue of cost.
My solution was to bring in two IBC totes which gave us about 550 gal of capacity. That increased the run time closer to 10 minutes. I interconnected the two tanks at the bottom, and plumbed the well to fill both at the same rate. Since there's not really enough pressure in the totes and air has to be able to be pushed out and sucked in I had to devise a different method to activate and deactivate the well pump.
First I needed a switch which detects when the tanks were low. Since both were the same size and received water at pretty much the same rate, I only have to check the volume in one tank -- making it a master and the other a slave tank. There are a number of different methods to detect the water level but I wanted to avoid sinking an electric valve into the tank. Therefore, I designed a float which controls a mechanical on/off switch on the outside of the tank for the empty condition and then used a typical float switch which detects the full condition on the inside at the top.
To monitor the empty and full switches, I chose a timer relay with a trigger input. It is powered by the full switch which turns on power to this relay as soon as the water level drops below full. By needing a trigger signal it sits and waits for the empty switch to trigger it. Once started the well pump will now run until this relay is turned off.
That condition will be met when the tank is full and power is removed from the relay. Now waiting for the water level to drop before once again receiving power to wait for the trigger signal.
Oh, and if you paid attention I left one thing out.
There is a second pump connected to the two IBC totes. That pump is the pump that fills the single 40gal pressure tank which feeds the faucets.
These are two electrically separate systems, operating independently. This is important to maintain simplicity and allowing each to have it's own purpose (function).
I stayed away from complex and electrical systems as much as possible to limited the points of failure and keep them easily replaceable. The most advanced part is the timer with a built-in trigger function which is inexpensive and readily available. (Yeah, I have spares for all parts.)
I mentioned a second pump. This was originally a used well pump left over from when I upgraded the old pool pump to a variable speed pump. The headroom on a well pump is pretty low but plenty to push water horizontally across the farm. Over time I replaced that with a higher end one which is able to deliver more water faster, leaving a pool pump as a backup.
In all the PVC plumbing, I ensure I use union couplings in such a way that I can replace any section; including removing and installing a new pump which might not align with the previous one. The valves use unions to connect each side of the valve. Unions are a great design; which makes life a lot easier!
For safety the well pump has a relief valve should the plumbing be blocked above ground. Of course, there is also a one-way valve (check valve) to prevent water from flowing back into the well.
In the end I have removed the original extra load (resistance) placed on the submersed pump by not plumbing into the pressure tanks but into the IBC totes. Configuring it to run well past two minutes ensures enough water is flowing through the electrical wiring housing to cool it back down. Having 500+ gallons cuts down on the number of times it is started. All these brings down the wear and extends the life of the pump.