Reverse Osmosis Membranes actually work better and produce better quality water the longer they are processing water. The answer is to buy the smallest membrane that will meet your water needs. The RO system will process water until the water storage tank is full and then the RO will shut off. This means the membrane will only produce enough water to fill the tank so a larger membrane will not necessarily produce more water, only fill the storage tank faster than a smaller membrane. This means that a smaller membrane will run longer to fill the tank and will produce better quality water and will last longer. Most under-sink RO systems only supply water to the drinking water faucet and maybe the refrigerator ice maker, so most people only need a 24 GPD membrane. If your RO system has a extra large water storage tank and feeds water to multiple appliances then you may need a larger membrane.
The flow restrictor works with the membrane to control the water flow and pressure across the membrane for the reverse osmosis process to work. The water flowing through the flow restrictor is the bad waste water that the membrane is discarding. So every time you replace the membrane you should replace the flow restrictor. Some flow restrictors are a small cylinder in line with the drain line coming from the membrane and sometimes the flow restrictor is a small tube inside the drain line coming from the membrane. When you replace the flow restrictor, you don’t necessarily need to replace it with the same type as long as you remove the old flow restrictor and replace it with the new one.
The flow restrictor and the membrane work together so it is important to make sure that the flow restrictor is sized for the membrane. This is why we always include the proper sized flow restrictor with our membranes. If you have purchased a membrane somewhere else and it did not include a flow restrictor, and need a replacement flow restrictor, please contact us and we will help you get the proper size.
When the RO system is processing water it is also rinsing the membrane to keep it clean. This rinse water is going down the drain. It is normal for the RO system to run for a couple hours and then stop. If the dripping sound continues for more than 5 to 6 hours or all day then you should call your water treatment professional to diagnose the problem.
If this sound is new to your system, the reason may be that crud has built up on the drain connection at the drain pipe and is causing the water to spray into the drain pipe. To quiet the sound you can try this; first turn off your RO system. Next, disconnect the drain tube from the drain pipes under the sink. Then clean the tubing connection and the tip of the tubing with a Q-tip. Re-connect the tubing to the drain pipe connection and turn on the RO system.
There are several reasons why an RO that was previously working properly starts to only produce only a small amount of water. The most common problem is the holding tank is not serviced properly. To properly service your holding tank see “How do I service the holding tank…?” The next common problem is clogged pre-filters or clogged automatic shut-off valve. Try changing the filters, next try checking for water flow before and after the automatic shut-off valve. The next common problem is that the membrane may need replaced.
The holding tank not only has a chamber to hold your drinking water but also has an air chamber to provide water pressure to the drinking water faucet. As the RO fills the tank with water the water compresses the air in the air chamber. the compressed air then can push the water out when the faucet is opened. In order for the tank to provide water pressure but not impede the RO from producing good quality water the tank needs to have just the right amount of air pressure in it. Just like your car tires and bicycle tires the tank will loose a small amount of air over time. To service your RO holding tank;
First, turn off your RO system, next open the RO faucet and let all the water run out. When the water stops running out of the RO faucet, lift up the water storage tank; if the tank feels very heavy then find the air valve on the side near the bottom of the tank. Attach a bicycle pump to the air valve and start pumping air into the tank. Water will start to come out of the faucet. Continue to add air until water stops coming out of the Ro faucet. If you hear air bubbles in the tank, remove the pump and depress the center of the air valve. If water comes out of the air valve then the tank is bad and needs to be replaced. Once all the water is out of the tank the tank should only weigh about 4 pounds. using a low pressure air gauge check the air pressure and adjust it to 10 psi. Turn on the RO system and let the tank fill with good quality water.