​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.

If your home receives water from a city or municipal supplier, your water has been treated at a local municipal treatment plant. So you may be asking, "Why should I worry about additional water treatment if the water already been treated at a water plant?" Municipal water suppliers do their best to protect the public. But contaminants [...]

Read More »


Every year, thousands of “BOIL WATER ADVISORIES” are issued in cities throughout the U.S. These “alerts” or “advisories” are issued when there is the actual or strong possibility of bacterial contamination in the drinking water. When the threat is large, like widespread contamination and power outages after a hurricane or even when the threat is [...]

Read More »


Preparing for Emergencies and Natural Disasters When an 8.1 magnitude earthquake shook Nepal earlier this year, entire mountain villages were flattened. Those who survived, struggled to find adequate food and water as they worked to rebuild their homes and lives. In recent years, we’ve witnessed the devastation and destruction left by earthquakes, fires, flooding, hurricanes and even [...]

Read More »


WARNING: Don’t Drink or Cook with the Water Realizing that you don't have access to clean, safe water for making ice, brushing teeth, washing dishes, or food preparation is enough to make most of us panic. If anything, it certainly heightens our awareness of how important water is in our everyday activities. While being told not to [...]

Read More »


A post in the New Yorker, entitled “The Really Big One” talks about the inevitability of a magnitude-9 earthquake off the Northwest coast. Reading this article really got me thinking, 'Am I (and my family) prepared if something like that were to really happen?' Seismologists talk about this huge earthquake and subsequent tsunami that they believe [...]

Read More »


In weighing the advantages and disadvantages of reverse osmosis, here are a few of the “pros”: Exceptional Water:  Because RO has the ability to remove 95-99 percent of total dissolved solids (TDS), as well as chlorine, fluoride and other impurities, reverse osmosis filtration can greatly improve the odor, appearance, and overall taste of your water.Quality Water Means Increased Water Consumption: Installing an RO system [...]

Read More »