CSV Operation While Pressure Tank being Filled

[Bubba]

Let's say you want to setup a 2 storey house with a CSV1A valve and 20 Gal. pressure tank and 50/70 pressure switch. I understand a 10 Gal. pressure tank is usually recommended in this case, but maybe you want to try and get the best of both worlds and also reduce the number of pump cycles from small demands when the pump is off and the pressure tank is still above its "turn on" pressure, so you go to a larger tank.

So if I understand correctly, in this case it will take the CSV valve 5 minutes to fill that pressure tank (1 gpm) after the last faucet is turned off (assuming the 20 Gal. pressure tank will hold approx. 5 Gal. of water).

What happens if for example the CSV valve is in the process of filling the pressure tank and someone turns a 2 gpm faucet on (when the pressure tank is only partially filled)? What does the CSV valve do? Does it go back to "full run mode" and stop filling the pressure tank, or does that faucet draw from the pressure tank until the pressure switch sends another "turn on" signal to the pump?

 

[LLigetfa]

So if I understand correctly, in this case it will take the CSV valve 5 minutes to fill that pressure tank (1 gpm) after the last faucet is turned off (assuming the 20 Gal. pressure tank will hold approx. 5 Gal. of water).

No. The tank may always being filled while the pump is running. The tank could be half full while the CSV is regulating the pressure.

 

[Sponsor]

 

[Reach4]

So if I understand correctly, in this case it will take the CSV valve 5 minutes to fill that pressure tank (1 gpm) after the last faucet is turned off (assuming the 20 Gal. pressure tank will hold approx. 5 Gal. of water).

If your CSV is set to 60 psi, and you have a 50/70 pressure switch, and the tank holds 5 gallons, at 1 gpm it would take about 2.5 minute to turn off. If you wanted shorter, you would adjust the regulation pressure to maybe 62 psi.

What happens if for example the CSV valve is in the process of filling the pressure tank and someone turns a 2 gpm faucet on (when the pressure tank is only partially filled)? What does the CSV valve do? Does it go back to "full run mode" and stop filling the pressure tank, or does that faucet draw from the pressure tank until the pressure switch sends another "turn on" signal to the pump?

The 3/4 full tank would drop to half full, and the CSV would regulate to 60 psi.

 

[Bannerman]

A CSV maybe used with any size tank but when using a smaller tank, less water will need to be utilized before the pump is activated to deliver constant pressure to fixtures.

With a 50/70 system with the CSV calibrated to 60 psi, water use will cause the system pressure to lower to 50 psi which will cause the pump to activate. Once the pump is activated, the CSV will fully open until sensing a rise to 60 psi on the outlet side whereby it will reduce water flow from the pump so as to maintain 60 psi downstream. Because the pressure tank is plumbed to the downstream side of the CSV, the pressure tank pressure will be also 60 psi, which will mean it will be 1/2 filled so a tank with 5 gallons fluid capacity will contain 2.5 gallons while the CSV is providing 60 psi to fixtures.

Once there is no further flow to faucets, to prevent exceeding 60 psi, the CSV will close completely, but as it is designed to 'leak' 1 GPM when closed, the pressure tank will continue to fill the remaining 2.5 gallons until 70 psi is achieved to cause the pressure switch to shut down the pump.

If further water is utilized while the pressure tank is continuing to fill, the system pressure will quickly drop to 60 or slightly less to cause the CSV to again open to maintain 60 psi downstream.

 

[Bubba]

A CSV maybe used with any size tank but when using a smaller tank, less water will need to be utilized before the pump is activated to deliver constant pressure to fixtures.

With a 50/70 system with the CSV calibrated to 60 psi, water use will cause the system pressure to lower to 50 psi which will cause the pump to activate. Once the pump is activated, the CSV will fully open until sensing a rise to 60 psi on the outlet side whereby it will reduce water flow from the pump so as to maintain 60 psi downstream. Because the pressure tank is plumbed to the downstream side of the CSV, the pressure tank pressure will be also 60 psi, which will mean it will be 1/2 filled so a tank with 5 gallons fluid capacity will contain 2.5 gallons while the CSV is providing 60 psi to fixtures.

Once there is no further flow to faucets, to prevent exceeding 60 psi, the CSV will close completely, but as it is designed to 'leak' 1 GPM when closed, the pressure tank will continue to fill the remaining 2.5 gallons until 70 psi is achieved to cause the pressure switch to shut down the pump.

If further water is utilized while the pressure tank is continuing to fill, the system pressure will quickly drop to 60 or slightly less to cause the CSV to again open to maintain 60 psi downstream.

OK I get it now, that makes sense. Excellent explanation, thanks!

 

[Bubba]

If your CSV is set to 60 psi, and you have a 50/70 pressure switch, and the tank holds 5 gallons, at 1 gpm it would take about 2.5 minute to turn off. If you wanted shorter, you would adjust the regulation pressure to maybe 62 psi.


The 3/4 full tank would drop to half full, and the CSV would regulate to 60 psi.

Yes, that makes sense. Thanks.

 

[Bubba]

Personally, if I try to envision our typical household use, I think a 10 Gal. pressure tank (~ 2.5 Gal. useable) might create an excessive number of pump cycles due to short, low demand calls for water. I believe each of these cycles will also have the typical "surge" of volume when the faucet is on, until the tank gets to 60 psi. I think I'd be willing to trade that for a little longer period of system pressure between 50-60 psi.

 

[Valveman]

Good explanation guys, thanks! So, you can see from the explanations, when used with a CSV the tank is basically a mechanical timer more than a water storage vessel. The amount of water you get out of the tank is irrelevant. The tank will only supply small uses of water like for ice makers and washing hands. Any longer uses will receive water directly from the pump and CSV. Your water does not come from the tank, it comes from the well and pump. The water is stored in the well, not the tank. The only purpose for a pressure tank is to limit the number of cycles, and when you have a CSV to do that for you, you don't need much of a tank.

It doesn't hurt for the pump to come on every time you use water. What is important is that the pump doesn't go off until you are finished using water. With the CSV filling the tank at 1 GPM, you can make it take 30 seconds, 60 seconds, or even 2 minutes to fill the tank, depending on the size of tank and the setting of the pressure switch. This mechanical timer only starts after you stop using water. When you flush a toilet, the 1 gallon in the 4.5 gallon size tank is used up as the pressure falls form 60 to 40 PSI. At 40 PSI the pump starts. The CSV keeps the pump running WHILE the toilet is filling. Once the toliet is filled the CSV starts filling the tank at 1 GPM. With the 4.5 gallon size tank the CSV continues to fill the last 1/2 gallon in the tank for an additional 30 seconds. With the 10 gallon tank it fill the tank for 60 seconds, and the 20 gallon tank for 120 seconds. During this 30, 60, or 120 second time, if someone elsewhere in the house uses any water, it drains the tank down and the mechanical timer starts again. The CSV is just slowly filling the tank, keeping the pump running, to make sure you are finished using water. If you are finished using water the pump shuts off after this amount of time. If anyone in the house is still using water the pump just keeps running until everyone is finished with the water, and then it still runs another 30, 50 seconds just to make sure.

The trick is not to have more water in a tank for hand washing, but to keep the pump from shutting off until everyone in the house is finished using water. Even a huge 80 gallon size tank only holds 20 gallons of water. Again, your water comes from the well, not the tank.

 

[Bubba]

It's amazing more people aren't aware of this, although it does take a bit of work to think through the logic and really get it.

My only concern was that if we're so intent on reducing pump cycles during "long demand" uses, why not also keep the number of cycles to a minimum for the small, short demands. But after your last comment above, I can see how even a 10 Gal. tank (2 storey house) would probably take care of many of those cycles.

 

[Valveman]

It's amazing more people aren't aware of this, although it does take a bit of work to think through the logic and really get it.

Yeah we only get the intelligent customers like you, or the ones who have had so many problems they will try anything, even though they don't understand how it works. Most people just blindly accept whatever the pump man is selling. The problem with that, is that even though there are a few good ones, the vast majority of pump installers know less about pumps than a bag of nuts. Lol! The worst ones will sell you whatever they make the most money on, even though they know a better and less expensive method. Years ago they just got a way with it. Today with the information available on the Internet people can make an informed decision if they take the time to research.

 

[Bubba]

That's what started this whole investigation to some degree. There are some very good plumbers around my area, but the one or two "well guys" made me think I was back in 1950 when I talked to them. I know there are a couple of well driller guys on this forum who really know their stuff, but in my rural area the well and pump guys are doing the same thing their "grandpappy" did 75 years ago. I just didn't trust the information I was getting.

Don't even get me started about the water filter/purification guys... That's the next piece of the puzzle I need to tackle.