CSV outlet and tank port the same chamber? Tank fill time questions...

[jasont]

 I'm trying to figure out if a tank with an 8 gallon draw down will require the pump to run for 8 additional minutes after fixtures are shut off or if it only needs to run for about 4 additional minutes?    I'm also trying to figure out if there is any advantage to tank fill rate whether the tank is connected to the tank port on the CSV1A valve or if the tank is connected via a tee shortly after the outlet port.

So assuming a 40/60 pressure switch and a CSV1A configured to 50 psi...
Is the tank hook-up outlet more of a convenience and is really the same as the service outlet? From the diagram of the valve internals it looks like they are tied to the same chamber.   Therefore, isn't the 1 gallon per minute rate only after fixtures are turned off and the tank will go from 40 to 50 psi at potentially greater than 1gpm while a fixture is open and only have the remaining 10 psi added to the tank at 1gpm when the fixtures are turned off.    Therefore if one has a tank with a 8g draw, the pump does not have to run 8 additional minutes after fixtures are closed, rather the pump would have to run about 4 minutes.   Am I correct?  If so I could adjust CSV1a valve to sustain 55 psi and reduce the pumps run time after fixtures are closed to approximately about 2 minutes.    Do I understand all this correctly?

[Cary Austin]

The CSV doesn’t do anything until the pressure reaches the set point of the CSV.  So with a 40/60 switch and a tank that holds 8 gallons, you could have from 1 to 8 minutes of tank fill time, depending on where you set the CSV.

With a 40/60 switch and the CSV set at 40, the fill time would be 8 minutes.  With the CSV set at 58 PSI, the fill time would only be 1 minute. 

As long as you are using more than 1 GPM the CSV will never let the pump shut off.  Only when you have turned off all the faucets will the 1 GPM minimum flow through the CSV start filling the tank.  If it fills from 40 PSI to 60 PSI at 1 GPM, it will take 8 minutes to fill the tank.  If it fills from the CSV setting of 58 PSI to 60, it will only take 1 minute to fill the pressure tank.

The ¾” port in the bottom and the two ½” ports on the side of the CSV1A are all downstream of the CSV.  It would be the same to attach to one of these ports, as it is to attach to a tee after the CSV.

A CSV will work with any size tank.  The larger the pressure tank the closer the CSV is set to the off setting of the pressure switch, to reduce tank fill time as needed.

[jasont]

That really solidifies my understanding, I think I got it and I'm liking this valve more and more.
So it sounds like I'll be setting the pressure switch to 58 then. 

[Cary Austin]

So it sounds like I'll be setting the pressure switch to 58 then.

No, set the CSV at 58 PSI since the pressure switch shuts the pump off at 60.  But I think that is what you meant. 

[jasont]

Yes sorry I misspoke, I meant CSV.  I wouldn't have actually made that mistake.

BTW, the diagrams show a pressure relief valve.   Is this a safety like the ones on a hot water tank, or is it one for regulating pressure to the csv?   Do you have a link to one to show me one that is appropriate for the setup we were discussing?

Thanks

[Cary Austin]

Yeah a pressure relief valve is just for safety in case the pump doesn't shut off when it should.  (bad pressure switch)  It should never relieve water unless there is a major problem.  You can install a pressure relief valve on any of the extra ports on the CSV1A, or anywhere in the system after the CSV.