Checking and Adjusting Your Reverse Osmosis Storage Tank Air Pressure

Why and When to Check Tank Pressure

• Ensure Proper Water Flow: An under-pressurized tank delivers water sluggishly. If you notice that the Reverse Osmosis Faucet has a weak, slow flow, the tank’s air charge may be low. Checking pressure can identify this issue.
• Maintain Tank Health: Over time, the Reverse Osmosis Tank bladders naturally lose some pressure. Topping up the air annually helps maintain the bladder’s elasticity and prevents it from staying “waterlogged.” If the tank loses pressure very quickly (needing air more than once a year), it may indicate a leak or bladder failure.
• Prevent Performance Problems: Both low and high air pressure can cause problems. Under-pressure means the tank won’t push out all its water, while over-pressure means the tank won’t fill properly. Regular checks (approximately every 12 months) keep the pressure in the ideal range (typically 0.5 – 0.8 Bar when empty) for smooth operation.

Tools and Materials Needed

Gather the following items before you begin:

• Pressure Gauge: A low-pressure tire gauge or digital gauge (0 – 1 Bar range) to measure the tank’s air pressure.
• Air Pump: A bicycle pump or hand pump to add air. (An air compressor can be used carefully on a low-pressure setting or with a regulator, to avoid over-inflation).
• Bucket or Container: For catching water when you drain the tank.
• Towel or Rag (Optional): To absorb any small spills.
• Pliers or Wrench (Optional): Helpful if you need to turn any stiff shutoff valves or disconnect the tank.

Before starting, ensure you have access to the tank’s air valve (usually a Schrader valve, similar to a bike tire valve, often located on the top or bottom of the tank and covered by a plastic cap).

Step-by-Step: How to Check & Adjust Reverse Osmosis Tank Pressure

1. Shut Off the Water Supply: Locate the feed water shutoff valve that supplies the Reverse Osmosis System (often under the sink). Turn it off to stop water flowing into the system.
2. Drain the Tank Completely: Open the Reverse Osmosis Faucet and let it run until water stops. This may take several minutes as the tank empties. Allow it to fully drain all stored water. Tip: Catch the water in a container so it’s not wasted (you can use it for drinking or plants).
3. Locate the Air Valve: Find the tank’s air valve (Schrader valve). It typically has a blue or black plastic cap covering it. Remove the cap to access the valve. Important: Keep the Reverse Osmosis Faucet open during this process so any additional water in the tank can exit as you add air. This ensures you’re measuring the air pre-charge, not trapping pressure against water.
4. Check the Tank Pressure: Using a pressure gauge, check the tank’s air pressure by pressing the gauge onto the Schrader valve (just like checking a bicycle or car tire). Only measure with the tank empty of water. The gauge should read in the range of about 0.5 – 0.8 Bar for an empty standard Reverse Osmosis Tank. If the reading is within this range, the pre-charge is already ideal. If it’s lower or higher, you will need to adjust it. (Note: If you momentarily depress the valve core and water comes out of the air valve, the tank’s internal bladder has ruptured or failed. In that case, the tank must be replaced, you will not be able to fix pressure by adding air).
5. Adjust the Pressure if Needed: If the pressure is below the recommended 0.8 Bar, use a pump to add air through the Schrader valve. Add a few short pumps at a time and re-check the pressure frequently to avoid over-inflation. You may hear or see a small amount of water being forced out of the open faucet as you pump, this is normal, as you are expelling any remaining water from the tank’s bladder. Continue until the the tank is empty and the gauge reads in the 0.5 – 0.8 Bar range. If the pressure is above the recommended range (e.g. someone overfilled it previously), release air by pressing the valve core (using a small screwdriver or the gauge tool) for a few seconds at a time, until the pressure drops back down and within the 0.5 – 0.8 Bar pressure range. Do not exceed 0.8 Bar.
6. Restore Service and Test: Once the tank’s air pressure is corrected, close the Reverse Osmosis Faucet and make sure the Schrader valve cap is back on. Then turn the main feed water supply on to let the Reverse Osmosis System refill the tank. Allow a few hours for the tank to fill completely. Finally, test the water flow at the Reverse Osmosis Faucet, it should be stronger and steadier if the pressure was the issue. When the tank is full, you can also verify that the system’s auto-shutoff valve works (it should stop producing water when the tank pressure reaches about 2/3 of the supply pressure).

Tips and Precautions

• Always work with an empty tank: Only check or adjust the air pressure when the tank is completely drained of water. The 0.5 – 0.8 Bar specification is the pre-charge pressure for an empty tank. If you measure the pressure with water in the tank, you will read the water pressure (which can be 2 – 2.7+ Bar when full) and get a false value.

• Avoid Over-Inflating: Adding too much air will reduce the tank’s water storage capacity and can prevent the Reverse Osmosis System from filling the tank properly. It can also risk damage to the bladder. Pump air in small increments and re-check with the gauge to hit the sweet spot . If using an air compressor, use a low-pressure setting or regulator to control the airflow.
• Avoid Under-Inflating: On the other hand, do not leave the tank with extremely low air pressure (or zero air). Insufficient air pressure means the tank won’t be able to push much water out. The tank might fill with water but then only trickle out a small amount because there’s not enough air to force the water to the faucet.
• Check Annually: Make it a habit to check the tank pressure about once a year (for instance, when you do yearly filter changes. Tanks can lose a little pressure over time as air permeates out, even without a leak. Regular top-offs help keep your water flow consistent. If you find you have to add air more than once a year, that may indicate an issue.
• Bladder Health: If you ever press the air valve and water sprays out, the internal bladder has failed (it’s allowing water into the air chamber). In this case, no amount of pumping will fix the issue, the tank will need to be replaced. Similarly, if the tank cannot hold the set pressure (loses air quickly again), the Schrader valve or bladder may be leaking.
• Safety: Always release water pressure (by draining the tank and opening the faucet) before removing the air valve cap or attaching a gauge. This ensures accurate readings and prevents water from spraying out while you work. Wear eye protection if you’re releasing air from a pressurized tank that isn’t fully drained. Also, be gentle with the Schrader valve core, just like on a tire, if it’s damaged it may leak air.

Signs of Under or Over Pressurization

Keeping an eye on your Reverse Osmosis System’s behavior can clue you in to tank pressure problems. Here are common symptoms of a tank that is under or over pressurized:

• Slow or Weak Faucet Flow: If your Reverse Osmosis Faucet only trickles or has very low pressure, it often means the tank’s air pressure is too low. The tank cannot push out water effectively. (Clogged filters or a spent Reverse Osmosis membrane can also cause slow flow, but if those are new, suspect the tank pressure).
• Tank Feels Heavy but Little Water: After you dispense water, pick up the tank (if it’s not fastened in place). If it still feels heavy even when the faucet ran dry and only a small volume of water came out, the tank likely was under-pressurized. In this case, much of the water stayed trapped in the tank because the air bladder wasn’t pushing it out.
• Runs Out of Water Quickly: If the Reverse Osmosis Tank seems to empty very fast (only a brief burst of water then it’s gone), that can be a sign of over pressurization. An overfilled air bladder (too high pre-charge) reduces how much water the tank can hold, so you get a strong initial flow that drops off quickly. The faucet may go from normal to dry after filling just a glass or two.
• Reverse Osmosis System Cycling On/Off Frequently: Incorrect tank pressure can cause the Reverse Osmosis System to “short cycle.” For example, an over pressurized tank will fill to shut-off very quickly with only a small amount of water, then as soon as you use a little water the pressure drops and the system turns back on, only to shut off again moments later. This rapid on/off cycle (if you have a booster pump, you may hear it start and stop often) is hard on the system. Under pressurization can cause the opposite problem: the system may run continuously because the tank never reaches the shut-off pressure. In either case, checking and correcting the air pressure can resolve these irregular cycles.
• Tank Not Filling to Capacity: If your filters and feed pressure are fine but the Reverse Osmosis Tank never seems to hold much water, check the air pressure. A tank pre-charged well above 0.8 Bar can prevent water from entering (the Reverse Osmosis Membrane can only push water in until the tank’s back-pressure is about 2/3 of the line pressure). The result is the system thinks the tank is “full” too soon. Reducing the air pressure to the proper range will allow the tank to fill with more water.

By following this guide and maintaining the correct air pressure (approximately 0.5 – 0.8 Bar when empty), you’ll ensure your Reverse Osmosis Storage tank operates at peak efficiency. Regular pressure checks keep your drinking water flowing strong and help prolong the life of the tank’s bladder and your overall Reverse Osmosis System. If you encounter persistent low flow or pressure issues even after adjusting the tank, consider other causes like clogged filters or low feed pressure.