If you have a reverse osmosis unit under the kitchen sink in Washington, the storage tank is the part most homeowners never check. It holds treated water between uses, and the air charge inside it decides how well the unit delivers water when the faucet opens. Checking that pressure is a simple, low-risk step you can do before you call anyone.

What the storage tank does

A reverse osmosis system pushes feed water through a membrane. The treated water goes to a small tank, where an air bladder keeps it under pressure. When you open the treated water faucet, that stored pressure pushes the water out. If the tank is low on air, the faucet may run slowly, sputter, or stop early. If the tank is full of water with no air cushion, the unit may seem to deliver nothing at all.

Before you touch anything

  • Shut off the cold feed water supply to the unit.
  • Open the treated water faucet at the sink until the flow stops and the tank is empty.
  • Find the air valve, which is usually the small stem on top of the tank.

Keep the system manual nearby if you have it. Many units list the factory air pressure on the tank label or in the manual. If you cannot find it, check the manufacturer's listing for your model number.

Reading the pressure

Use a standard tire gauge on the air valve, and read it with the tank empty. The reading should match the factory value. If it is well below that, the bladder may have lost air or the valve may be leaking. Add air slowly with a hand pump, rechecking as you go. If the gauge reads zero, or the valve hisses when you press the gauge on, the bladder may have failed and the tank will need replacement.

Signs the tank is the problem

  • Treated water flows well for a moment, then slows quickly.
  • The faucet drips after you close it, or water comes out of the tank valve.
  • Filter changes are current, but output is still weak.

Checks that come first

Before blaming the tank, rule out simpler causes. Make sure the feed supply valve is fully open. Look at the prefilter and membrane cartridge dates, since clogged filters reduce output on their own. Check the drain line for kinks, which can slow how fast the unit refills. Also confirm that water flow is normal at other taps in your home. A weak house supply will weaken the whole system.

Hard water and what it means for the tank

Washington tap water is described in local water reports as very hard, and that matters for the membrane and prefilters upstream of the tank. Scale and iron can shorten filter life, which indirectly affects how often you need to check the system. Homes on private wells in the Franklin County area may see heavier iron and hardness, so prefilter checks may need to happen more often. Tracking filter changes in a simple log helps you tell whether lost output comes from a filter issue or a tank issue.

When to stop and get help

If the tank loses air quickly after you refill it, or water comes out of the air valve, the bladder has likely failed. Shut off the feed water and stop using the unit until you can confirm the problem. If you plan to ask a service provider to look at it, keep the old tank parts and take photos of the labels, since these help identify the right replacement.

Keeping notes

Write down the date you checked the tank pressure, the reading, and any filter changes. A short log shows whether the tank holds its air over months, or whether a drop signals a larger change in your water. Keep the log with the system manual so the next person in the house can read it too.