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Hankelec

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- TL;DR Summary
- Adjustments needed to equalize volume of water in tanks at differing heights.

I am working on a reverse osmosis water system. There are 2 bladder type pressure tanks for storage. One tank is at floor level, the other tank is supported directly above the lower tank 5 feet above the floor. It would be advantageous if these tanks would fill at an equal rate, or approximately equal rate, from a single supply line coming from the RO system. And perhaps they will if I have both tanks pressurized equally and accurately at the same pressure.

The supply is 1/2" plastic. It enters the lower tank at floor level. Just prior to entering the lower tank there is a T junction which travels upward to the upper tank. Let's say the initial pressure of the tanks is set 2 psi below pressure pump kick-in pressure. Kick-in pressure equals 30 psi so empty tank will be pressurized to 28 psi. Kick-out pressure is 50 psi. So I will have a 5' column of water adding a psi or two that will need to be overcome to allow water to enter top tank.

As the top tank begins to accept water, there will be the 5' differential affecting the resistive pressure at its filler inlet. As the top tank's volume increases and its water height increases, will there be developed enough pressure difference relative to the bottom tank that will prevent water from entering top tank.

If supply water tends to oscillate from entering bottom tank then top tank, that is acceptable. What would not be favorable is if bottom tank fills to 30 gallon capacity and top tank is holding only 5 or 10 gallons. So what I am searching for is an offset pressure to best fill each tank to capacity. A 10% error factor is OK.

The supply is 1/2" plastic. It enters the lower tank at floor level. Just prior to entering the lower tank there is a T junction which travels upward to the upper tank. Let's say the initial pressure of the tanks is set 2 psi below pressure pump kick-in pressure. Kick-in pressure equals 30 psi so empty tank will be pressurized to 28 psi. Kick-out pressure is 50 psi. So I will have a 5' column of water adding a psi or two that will need to be overcome to allow water to enter top tank.

As the top tank begins to accept water, there will be the 5' differential affecting the resistive pressure at its filler inlet. As the top tank's volume increases and its water height increases, will there be developed enough pressure difference relative to the bottom tank that will prevent water from entering top tank.

If supply water tends to oscillate from entering bottom tank then top tank, that is acceptable. What would not be favorable is if bottom tank fills to 30 gallon capacity and top tank is holding only 5 or 10 gallons. So what I am searching for is an offset pressure to best fill each tank to capacity. A 10% error factor is OK.

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