A big pressure tank is good for lots of little intermittent uses of water like ice makers and toilet flushes as an 80 gallon size tank will deliver 25 gallons before the pump must start. Then if you have any long term uses of water like heat pumps or sprinklers, the CSV takes over after the pump starts and delivers constant pressure without letting the pump cycle on and off. For many years I believed that a big pressure tank with a CSV was the best of both worlds.
However, I have learned that the CSV takes out so many cycles for long-term uses of water, a small tank causing a pump cycle every time a toilet is flushed by itself, doesn’t add up to much. If the pool is filling, a sprinkler is running, or any other water is being used when a toilet is flushed, the CSV just gives a little more water for the toilet, but there is no extra cycle.
Seldom is a toilet flushed by itself. Usually within a minute after flushing, the shower or a sink will be turned on. Many times there will be two or three flushes within a minute of each other, then the shower or sink. And that is just one persons use. Multiple people in a house use water at the same time. Someone in the kitchen runs the sink or the dishwasher. Maybe the cloths washer has been on the entire time all this other stuff was happening. As long as some water is being used anywhere in or outside the house, the CSV makes the water go right past the pressure tank, straight to the faucet that is open. So it doesn’t matter if the tank holds 1 gallon or 25 gallons.
We have found that only systems that supply between 3 and 50 houses will benefit from a larger tank with the CSV.
Number of houses Size of Pressure Tank
Less than 2 Houses 4.5 gallon
3- 10 Houses 20 gallon
11-49 Houses 80 gallon
50+ Houses 40 gallon
Another counter intuitive thing about a CSV is, the more water a system uses, the smaller the tank can be. When you have less than two houses with multiple people using sinks, toilets, showers, appliances, etc., and/or a heat pump, sprinkler system, which includes garden hoses, a 4.5 gallon tank is all you need.
However, there are times when a little larger pressure tank can be beneficial. A large CSV controlled pump system can use an 80 gallon size pressure tank to supply an entire city of 40,000 people. So there is no reason to use a tank any larger than 4.5 gallon size for one or two home.
But when 3 to 50 homes are using the same pump system, a little larger tank can be a benefit. With 3 to 50 homes there are times when no one is using water, but there are enough connections that a few leaking faucets could be supplied by a pressure tank, so the pump does not have to start to supply a few leaks. In situations like these, a 20 to 80 gallon size pressure tank that holds 5 to 25 gallons of water would be good to use with a CSV.
To see the benefits of a smaller pressure tank see, “Why a Small Pressure Tank is All You Need with a CSV”, at this link.
http://cyclestopvalves.com/smf/index.php?topic=1953.0See this graphic;
http://www.cyclestopvalves.com/simple/home.phpThe Cycle Stop Valve system is on the top. A conventional tank system is on the bottom. If you turn on a sprinkler and let it run for hours, the pump runs constantly for hours as well. During this time, if you flush a toilet, take a shower, or use any other water, the pump is already running and the CSV just opens up a little to give you enough extra for the added shower. When you turn off the shower or the toilets fill and shut off, the CSV just resets to the amount of water needed to run the sprinkler.
The same thing happens when you turn on a shower. As long as the shower is on, the pump is also on, so even 40/11 toilet flushes don’t add a single extra cycle to the pump. In a house where there are multiple people, and/or multiple systems using water, the pump will be running a lot of the time, which is a good thing. As long as somebody, or something, somewhere in or around the house is using water, the pump is already running. Anything else turned on just gets the extra water it needs, without the pump having to cycle one extra time.
If you noticed the conventional pump system at the bottom of the graphic, it is just cycling on and off continually no matter where or how much water is being used.
The Cycle Stop Valve just lets you use as much or as little water as you want without cycling the pump. Water just goes from the pump, right past the tank, straight to the sprinklers, showers, wherever, because the CSV gives only the exact amount of water needed.
But don’t get me wrong. The CSV will work with any size tank you prefer. Some people think a larger pressure tank will give them a little stored water for times when the power is off. This is true if you are lucky enough that the power goes off while the tank is full. However, Murphy’s law says the 40/60 pressure switch will be at 41 PSI when the power goes off, and the largest tank available will be empty. A couple of 5 gallon jugs in the closet is a more reliable way to have some water when the power goes off.
