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7 Reasons For Reverse Osmosis Tank Not Filling Up (And Solution)

Scott Winfield
Last Updated on
by Scott Winfield

Reverse Osmosis tanks come in smaller sizes for drinking water and larger versions that act as water pumps for your home. The real benefit of this tank that sets it apart from others is its ability to clean water on a molecular level.

Despite the many benefits of reverse osmosis tanks, several issues can arise. Fortunately, with each of these reasons for why your tank won’t fill up, there are also solutions to how you can fix them.

Is Your Tank Filled with Water?

Is Your Tank Filled with Water

Not enough water is one of the more manageable issues to fix concerning your RO tanks. An empty tank is self-explanatory in the sense that it cannot filter water if there is no water in the tank.

It becomes more complex if you are filling your tank with water and it is going too quickly or leaking out, but both of these issues are separate ones.


Make sure your tank has water. If you are doing so and other issues are still occurring, there is an issue with the tank itself, and you should look for any leaks or cracks.

Is Your Tank Pressurized Properly?

Is Your Tank Pressurized Properly

Your tank’s pressure is crucial to it working correctly and supplying you with the proper amount of filtered water each day. It requires a specific amount of pressure to pump water through the tank to your home, and without it, it can lead to a lack of water and other issues.


As far as solutions go, if it has been a year since you purchased your reverse osmosis tank and the problems are arising now, chances are you have to repressurize.

Tanks should be repressurized every year by using a bike pump or air compressor. Your tank, depending on size, will have a specific PSI limit that you should reach. Once you reset it, you really should be set for the following year.

If your tank’s pressure is wavering or you’re not getting the correct amount of water, you will likely need to reset it. For example, you’ll know by the pressure being supplied to your sink or wherever you have your reverse osmosis tank if the water being supplied is too light or too heavy in force.

To release pressure, all you have to do is turn a valve on the tank itself. To add pressure, go back to your bike pump or compressor and add some. There should be an indicator on the tank that will read the pressure levels to you.

Does Your Water Have a Bad Odor or Taste?

Does Your Water Have a Bad Odor or Taste?

If the water from your reverse osmosis tank has a rotten egg smell or tastes awful, you most likely have hydrogen sulfide gas in your tank. The sudden presence of this gas happens when bacteria builds up in your tank and emits the horrible scent and taste you are experiencing.  

Reverse Osmosis Tanks use pressure to separate and filter the water within the tank, removing the contaminants and locating them on one side and the freshly cleaned water on the other. The side with the non-safe drinking water is deposited and sent away, but this doesn’t mean some can’t linger.

This issue happens more often in other water tanks and not as often in reverse osmosis tanks because of how contaminants are dealt with in RO Tanks. However, if it does occur, the solution to this problem is quite simple.


First, do not drink it. Second, you should dump the contaminated water inside the tank, clean it, and refill it with fresh water. If you’ve just caught a slight whiff of something off in your water, you probably caught it at the right time.

If you are looking to never have to deal with this issue again, cleaning your tank after every use would help, but that would also require repressurizing it every time.

If this odor appears more frequently than it should, there are other filters you can add to your tank to help with the issue.

Is Your Tank Making Loud Noises?

Is Your Tank Making Loud Noises?

For this problem, the critical signifier that something is wrong is what kind of sound you are hearing coming from the tank.

It’s common for reverse osmosis tanks to make some noise while filtering water. That only means it is doing its job.

However, if your tank is loud, maybe even making scary noises that sound unsafe, there are a few things that could be wrong. The main one being the pressure is off, and there is too little or too small of an amount compared to the water it’s dispersing, or the pressure is unstable.

It could also be that low-voltage or high-voltage switches cannot be closed, in which an alarm will sound, or that water found its way into the transformer of the tank’s purifier.

There are many possibilities as to what is making the loud noise in your reverse osmosis tank. The question then becomes, how do you fix it?


If the issue is the pressure, then the answer is simple.

If you believe the pressure is too low, you must dump the water and repressurize the tank. On the other hand, if the pressure is too high, you can use the valve on the tank to lessen it.

The voltage issues and the water infiltration in the transformer are out of your control. Unfortunately, there is not much that you can do on your part to fix this.

The noise coming from your working tank will happen no matter what. However, if you believe it is too loud, sound barrier technologies are available to lessen the noise if you see fit.

If the noise is bothersome or you think there is something wrong with the transformer, your best solution is to contact a plumbing professional who specializes in reverse osmosis tanks.

Is Your Tank Leaking?

Is Your Tank Leaking

If your tank is leaking in your reverse osmosis filtration system, there is most likely an air gap that can allow contaminants into your water. Unfortunately, air gaps are tricky because they are hard to spot and a pain to fix, solely because of the only way of preventing them.

The way to prevent this starts at the beginning.


The only way to avoid this problem comes by installing the tank properly. If you have to leak from an air gap, you did not install it correctly. You have to uninstall and reinstall your reverse osmosis tank to fix it.

Is the Water Running in Your Tank Too Slow?

Is the Water Running in Your Tank Too Slow?

There are several reasons why your reverse osmosis tank may be working too slowly at providing you with the clean water you need daily.

There may be a clog in your filter, the Reverse Osmosis Membrane is clogged, your pressure is too low, or there is a kink in the water line attached to your tank. Unfortunately, these sorts of things are bound to happen eventually to most tanks. Luckily, they are usually simple to fix.


The easy fix issues revolve around the tank filters and membranes. It is as simple as replacing them. Fortunately, these issues are typical for old filters. Therefore, you should only replace these filters every year or two.

Same with too low of pressure as the previous problem, you just have to repressurize your tank to fix it.

If the issue lies in the water line, double-check your tank, but ultimately, all you have to do is fix the water supply valve.

Is Your Tank Draining Too Quickly or Not Shutting Off?

Is Your Tank Draining Too Quickly or Not Shutting Off

It’s normal, even necessary, for your reverse osmosis tank to drain the contaminated water. Yet, the issue arises when the water is continuously draining, even hours after use. Too much draining becomes an issue because all your water is draining, leaving you with barely any water or a non-working tank.


The answer to this problem pertains to the parts of the tank where the water passes.

If it’s the check valve within your tank, the piece that filters the freshwater from the contaminated water, then it needs to be replaced. With this valve broken, your tank is constantly draining water.

It could also be the ASO, the automatic shut-off valve, which would also need a replacement.

You can run tests at your home to decide which one is the broken one, and once you do that, your tank should be back to normal.

If you shut off the water to your tank but can still clearly hear water running, the check valve is most likely the issue. If no water is flowing, but your tank is still draining too quickly when it’s on, then the ASO is the issue.

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Scott Winfield
Scott Winfield
My name is Scott Winfield and researching and writing about water filters and other strategies to purify water has become my full time passion in recent years. I'm glad that you found our site and you can look forward to authoritative and well researched content here to help you get the best in water.
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