Pump System Questions and Answers > Frequently Asked Questions
Can I use a Large Pressure Tank with a CSV?
Cary Austin:
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=1953.0
See this graphic; http://www.cyclestopvalves.com/simple/home.php
The 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.
MutantMonk:
What about pump heat dissipation if there are many very short cycles during the day?
For most single residential applications is there much difference in outcome between using a tank with a draw down of 3.2 gallons vs a tank with a draw down of 5.5 gallons?
Most of the available small 3,4,5 6 gallon tanks come with a very low preset pressure. I have one of these tanks and use it with my CSV1. I increased the preset to 45 lbs and it seemed to work well... what would you suggest I set the tank pressure to? I would like to run my system at 60psi to 80psi. Any suggestions would be welcome.
Thanks,
Leonard
Pittsburgh
Cary Austin:
--- Quote from: MutantMonk on September 12, 2014, 10:40:16 PM ---What about pump heat dissipation if there are many very short cycles during the day?
For most single residential applications is there much difference in outcome between using a tank with a draw down of 3.2 gallons vs a tank with a draw down of 5.5 gallons?
Most of the available small 3,4,5 6 gallon tanks come with a very low preset pressure. I have one of these tanks and use it with my CSV1. I increased the preset to 45 lbs and it seemed to work well... what would you suggest I set the tank pressure to? I would like to run my system at 60psi to 80psi. Any suggestions would be welcome.
Thanks,
Leonard
Pittsburgh
--- End quote ---
It is motor heat dissipation that you are talking about. There is usually a 1 minute minimum run time and off time for the motor to dissipate heat caused on start up. However, with a CSV the motor is running and especially filling the tank at reduced rate and reduced amperage. At reduced amperage the motor load is "de-rated", which means it doesn't have as much heat to dissipate and doesn't need the 1 minute minimum tank fill time.
With a 60/80 pressure switch you would want about 55 PSI air in the tank.
MutantMonk:
Wow!
Thanks for responding.
Not to be argumentative but since I first asked this question, I found somewhere on this forum (I think), that the tank pressure should be set 2 psi below the pressure switch cut in pressure?
So that would require the tank pressure to be set at 58 for a 60/80 system... again I am not trying to be argumentative here… just want to make sure I am understanding correctly.
I have been using a CSV1 for the last 8 years and it is truly manna from heaven. I have been running it with a tank preset at 45psi and tank draw down of 5 gallons with a pressure switch set at 50/70.
Will a CSV150 work with a 60/80 system pressure
What are the different applications for the CSV140 the CSV150 and the CSV160?
My other question was... is there a significant functional difference between a tank with a drawdown of 3.2 gal vs one with a drawdown of 5.5 gal.
Are there any, out of the ordinary, tank specifications when using tanks with a Cycle Stop Valve; i.e. using a tank that is used with a reverse osmosis system
Do you know if Cycle Stop Inc. sells their small pressure tank individually?
That’s a lot of questions sorry.
Regards,
Leonard
Pittsburgh
MutantMonk:
Who, how and what controls the "1 minute minimum run time and off time"?
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