I have a cistern pump and tank. The tank is 20 gal. Can I replace it with a 5 gal tank

[Brad clark]

I have a cistern pump and my tank is 20 gal. Would it hurt to replace with a 5 gal tank and what difference would it make. I have a small cabin. I very rarely use water. I have I sink, 1 toilet, and 1 shower? Thank you

 

[Valveman]

A 20 gallon size tank only holds 5 gallons of water. That tank is probably already too small to get 1 minute of run time for the pump, which is the minimum required. A 5 gallon size tank only holds 1 gallon of water. This would make your pump cycle on and off rapidly, which is not good. A 4.5 or 5 gallon size tank is all you need when working with a Cycle Stop Valve. But without a CSV you want the tank large enough to make the pump run for at least 1 minute.