Read Between the Lines: Only Way to Get the Truth
Cycle Stop Valve verses Constant Pressure Pump video
CSV verses VFD demo
What is NOT said in articles and advertisements sometimes can be the best place to discover the truth. We must read between the lines and look at things from different angles to uncover the facts.
One recent example is an advertisement that explains the benefit of a tank that is specially designed for use with Variable Speed Pumps or VFD's. The ad claims this tank solves the biggest problem with VFD's, which is stagnant water. They go on to further explain that newer VFD's activate the pump quicker than ever, and that pressure may only drop from 2-5 PSI. A diverter circulates water in the new tank while the pump is running. This eliminates the water in the tank from becoming stagnant and is really a good idea.
Looking at these statements from a different point of view, you might see another problem. If a special diverter is needed to circulate water in the tank when using a VFD, water in the tank is never used. No water ever goes in or comes out of the tank, because the pump is always operating at a constant 50 PSI. If no water ever comes out of the tank, then every time the icemaker fills the pump must come on. Every time a toothbrush is washed the pump must come on. The pump must start for every flush or even a single glass of water. If the system were allowed to drop from 60 PSI to 40 PSI before the pump was started, a certain amount of water would be expressed even from a small tank. At 50 PSI constant, you would get the same amount of water out of a 1 gallon tank as you would from a 1,000 gallon tank, which is NONE, ZERO, ZILCH, NADA.
Reading between the lines will tell you that the same thing that causes water in the tank to become stagnant can also cause:
1) the pump to start every time a faucet is cracked open which could be hundreds of cycles per day.
2) the pump to repeatedly start and stop thousands of times a day for a dripping faucet, or a "forgot to giggle the handle" toilet. This could ultimately cause the system to fail, which would be more of a problem than a little stale water.
In a recent article about down hole check valves the need for more clearance was expressed. This added clearance between the movable part of the check valve and the body is needed to prevent sand and debris from locking up the check valve. It was reported that the NGWA and the EPA say an acceptable amount of sand is about 1/2 of a teaspoon in 20 gallons of water even in wells for potable use. Many pump companies design sand handling characteristics into their pumps as well as there check valves.
Reading between the lines, you could determine that it is important for all parts of pump system, to be able to handle some sand. These same companies who are concerned about their pumps and check valves handling sand also make control valves, which are better known as "constant pressure valves". These "constant pressure" valves are installed at the surface which could be hundreds of feet above the pump and check valve. These "constant pressure" valves screen all the water through a 20 mesh screen and also have a tiny bypass hole drilled through the outlet. The same sand that can lock up the down hole check valve will also clog the 20 mesh screen or the tiny bypass hole which is solely responsible for the cooling of the pump and motor. When either the 20 mesh screen, or the tiny drilled hole become clogged the pump and motor will ultimately be destroyed from a lack of cooling flow. These companies tell us that the screen and drilled hole in a "constant pressure valve" are not a problem. Either we have got sand in the water or we don't. If we have sand or debris then every component of the pump system from the pump to the controls must be able to handle sand. If we do not have sand then why are we concerned about the sand handling characteristics of the pump or the check valve? Which is it guys? Do we plan for sand and debris or not?
Another recent article by Amtrol compared "constant pressure valves" to "variable speed pumps" and ordinary pressure tank systems. Their conclusion was that "constant pressure valves" and "variable speed pumps" used twice as much power as the ordinary pressure tank system. They also concluded that the "variable speed pumps" cycled on many times a day, and that "constant pressure valves" only reduced the number of cycles per day by a small amount over standard pressure tank systems.
Again we must read between the lines. Looking at the set up for the test we see that only 320 gallons per day was used for showers and sinks. A real test of "constant pressure" would have at least turned on a garden hose with a sprinkler or used a heat pump, drip system or some other use which would require a steady output of water for 8, 12, or even 24 hours a day. Changing the test to a more real world application such as running a 5 GPM sprinkler for an extended amount of time would completely change to results. With this continuous use of 5 GPM the pressure tank only system would cycle hundreds of times per day and use more power than either the "variable speed pump" or the "constant pressure valve" either of which would only cycle the pump one time. Why would we even test "constant pressure systems" on a house that doesn't have any continuous demands for water. Which is it guys? Do houses have garden hoses, sprinklers, heat pumps, or not?
Any company will tell you the good stuff about their product. Listening to what is NOT being said or reading between the lines can be the best way to keep yourself out of trouble.