Vertical trigger float valve

[Valveman]

OK you need to understand how the pump works. If you have a 10 GPM well pump (guessing), without a Cycle Stop Valve the well pump will always pump 10 GPM or it is off. If the float valve filling the cistern only lets in say max of 7 GPM and reduces to 1 GPM as the tank fills, the well pump will be cycling on and off between 40 and 60 over and over until the cistern is full. You need a cistern fill valve than can be adjusted for a set amount (10 GPM) of flow to keep the well pump from cycling on and off. Without a Cycle Stop Valve on the well pump, any use of water less than 10 GPM will cause the pressure tank to fill and drain as the pump cycles on and off, which is not good.

If you add a Cycle Stop Valve to the well pump, it will vary the pump flow rate from 10 GPM down to 1 GPM as needed. But even then a regular float valve can finish filling the cistern at less than 1 GPM for long periods of time. When using a CSV, any water use less than 1 GPM will cause the pump to cycle on and off. So, a CSV will greatly help with a regular modulating type float valve. The CSV would not let the well pump cycle on and off until the float valve regulated the flow to less than 1 GPM. But I still prefer a non-modulating valve of some kind to let the cistern fill faster, saving energy and money, as well as keeping the well pump from cycling on and off.

Your irrigation maybe set up to use 10 GPM on every zone, which is the way we use to keep pumps from cycling during irrigation. Adding a CSV will still allow the use of big 10 GPM zones, but will also allow zones to match the yard instead of the pump and small zones down to as little as 1 GPM can be used without cycling the pump to death.

Same thing about cycling applies to the booster pump drawing water out of the cistern.

 

[wpns]

The filling of the tank works perfectly fine - its just wanting the line valve to close once the water reaches a specific level

So it works fine or it doesn’t shut off properly? Filling a cistern with a mechanical float valve just doesn’t work very well, which is why valve man and I are trying to encourage you to use something else.

 

[Valveman]

Most systems are set up like this where the well pump is dedicated to only filling the cistern. When a float switch is used instead of a pressure tank or pressure switch to control the well pump, the pump only cycles once to fill the cistern. Many people use this method to eliminate multiple cycles on the well pump to make it last longer. But when you want to use water on demand from the well pump as well as fill a cistern, a couple of technical issues need to be considered to keep the well pump from cycling to death while filling the cistern from a regular pressure tank controlled well pump.

 

[rustic_philosopher]

But when you want to use water on demand from the well pump as well as fill a cistern, a couple of technical issues need to be considered to keep the well pump from cycling to death while filling the cistern from a regular pressure tank controlled well pump.

This is indeed my use case:
well pump -> pressure tank -> house
-> float valve -> cistern -> submerged pump -> cistern pressure tank -> irrigation lines

So what are those "technical issues" you said need to be considered - I believe you but it's unclear what issues your referencing. I follow your thoughts on just general pump cycling based on water usage but I don't see how washing dishes or clothes is different from the cistern - maybe I am being obtuse hence my questions.

 

[rustic_philosopher]

So it works fine or it doesn’t shut off properly? Filling a cistern with a mechanical float valve just doesn’t work very well, which is why valve man and I are trying to encourage you to use something else.

Well, the original issue was just how to get the valve to work with the variable water level that I mentioned. Last year yeah the float worked just fine for keeping the cistern filled from the main pressure tank.

 

[rustic_philosopher]

OK you need to understand how the pump works. If you have a 10 GPM well pump (guessing), without a Cycle Stop Valve the well pump will always pump 10 GPM or it is off. If the float valve filling the cistern only lets in say max of 7 GPM and reduces to 1 GPM as the tank fills, the well pump will be cycling on and off between 40 and 60 over and over until the cistern is full. You need a cistern fill valve than can be adjusted for a set amount (10 GPM) of flow to keep the well pump from cycling on and off. Without a Cycle Stop Valve on the well pump, any use of water less than 10 GPM will cause the pressure tank to fill and drain as the pump cycles on and off, which is not good.

If you add a Cycle Stop Valve to the well pump, it will vary the pump flow rate from 10 GPM down to 1 GPM as needed. But even then a regular float valve can finish filling the cistern at less than 1 GPM for long periods of time. When using a CSV, any water use less than 1 GPM will cause the pump to cycle on and off. So, a CSV will greatly help with a regular modulating type float valve. The CSV would not let the well pump cycle on and off until the float valve regulated the flow to less than 1 GPM. But I still prefer a non-modulating valve of some kind to let the cistern fill faster, saving energy and money, as well as keeping the well pump from cycling on and off.

Your irrigation maybe set up to use 10 GPM on every zone, which is the way we use to keep pumps from cycling during irrigation. Adding a CSV will still allow the use of big 10 GPM zones, but will also allow zones to match the yard instead of the pump and small zones down to as little as 1 GPM can be used without cycling the pump to death.

Same thing about cycling applies to the booster pump drawing water out of the cistern.

If I understand though (I may not), the CSV thing is a general use thing regardless of the cistern or not as the scenario is describes happen with daily usage in the house. I am unclear on why its particular interest for the cistern?

EDIT: To further explain my confusion - it sounds somewhat like the concern is around the last filling of the cistern but even if a valve slowly fills the last bit of a cistern, say 10 gallons over 2 hours that isn't going to trigger the pump to come on even once as the water in the pressure tank is going to be there to supply that without refill / triggering the pump.