​How Long Does it Take to Fill a Reverse Osmosis Storage Tank?

Posted by
Freeman Linton

How Long Does it Take to Fill a Reverse Osmosis Storage Tank? The short answer is it typically takes 2 to 4 hours to fill a standard reverse osmosis tank (2.8 gallons or 10.6 L).

Because the reverse osmosis filtering process takes time, storage tanks are a necessary component with any RO system. Without a storage tank, you would probably have to wait 5-10 minutes just to fill a glass of water. With a storage tank, you can quickly fill your glass, pot, or water bottle.

RO holding tank fill rate will vary depending on three factors:

  1. The Type of RO system you have will impact how quickly water will fill your tank. For example, the Watts Kiwk Change RO System is designed to produce 100 gallons of water per day. The PuROTwist 4-Stage RO System produces 50 gallons of water per day. This means that the 100 GPD system will replenish the water storage tank twice as fast a 50 GPD system.
  2. Incoming water pressure. The ideal water pressure for most RO system to operate efficiently is 60 psi, but should operate properly between 40 and 80 psi. When your household water pressure is low (near or below 40 psi), water cannot be pushed through the RO membranes to produce filtered water. You may need to add a booster pump to your RO system to increase the incoming water pressure to the RO system.
  3. Age of your filters. Clogged filters can cause your RO tank to fill VERY slowly. Filters need to be changed every 6-36 months, depending on the filter. When filters become fouled or clogged, the flow rate can slow to just a trickle. So, check your filters first.

Learn more about how RO filtration works

Keep in mind that as water is pushed from the storage tank to the RO faucet, the system will begin to produce more filtered water to refill the tank. That is why even after you’ve filled up your glass of water, you may still hear noises below the sink--indicating the system is now producing water and refill the storage tank.

Related Blog Posts and Links:

5 Reasons You May Have Slow Flow Rates From Your RO System

Determine exactly how much water your RO system is producing over a 24-hour period.

RO Troubleshooting Guide for answers to other common concerns.