Written by: Gene Fitzgerald // Last Updated: Mar 14, 2023
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RO tanks operate under pressure to avoid the need for a pump to push water from the tank up to the faucet. The tank’s internal pressure needs to be maintained within a specific range for the system to function.
4-gallon RO storage tanks operate in the same fashion as any other sized tank, so the pressure must be monitored and repressurized if it drops too low. Storage tanks will gradually lose pressure over time, so this is something worth learning to do before your tank stops working.
Let’s take a closer look at everything you need to know about 4-gallon RO tank pressure including how to repressurize such a tank.
Key Takeaways
The size of the tank doesn’t make much of a difference when it comes to the ideal air pressure inside a reverse osmosis tank. Generally speaking, these tanks should be kept within 6 to 8 psi when measured empty.
This is just a general recommendation though, so be sure to check your tank’s label or product manual for the precise number.
The pressure in a full 4-gallon RO tank will be around ⅔ of the feed water pressure in your home. In other words, the higher the pressure in your plumbing system, the higher the pressure of your storage tank when full. For example:
Pressurizing a reverse osmosis tank is a fairly simple process that only requires a few basic household tools you likely already have lying around.
All you need are the following tools:
Have everything collected?
RO tanks lose pressure for the same reason bicycle or car tires gradually lose pressure over time: Air will seep out of the tank given enough time, at which point you’ll start to notice that the water coming out of your RO faucet is flowing slowly.
The good news is this is a normal function of the storage tank, so there’s no need to worry. If you start noticing the tank is losing pressure rapidly, this is indicative of a more serious issue like a ruptured tank bladder, which requires replacing the tank entirely.
4-gallon RO tanks – like all RO tanks – are hydropneumatic, which means they operate under pressure and can send pressurized water whenever needed. Hydropneumatic tanks contain both an air and water chamber inside them separated by a rubber bladder.
Because RO systems are slow at filtering water, a storage tank is required to keep enough water on hand to fulfill your needs. Without a tank, you would be waiting around for 5 minutes or more every time you needed to fill a glass.
Another important function of the tank pressure is triggering the automatic shut off valve (ASO). This is the valve that tells the system to stop filtering water when the pressure in the tank reaches a certain level. Without this valve, your reverse osmosis system would continuously produce water and dump it down the drain – wasting an excessive amount of water.
If you have any questions about 4-gallon RO tank pressure please don’t hesitate to leave a comment below!
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