Reverse Osmosis Check Valve Installation Guide

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The check valve is a small but crucial component in the operation of a reverse osmosis system.

Without it, water can flow back into the reverse osmosis membrane from the storage tank, compromising the performance of the system and potentially causing serious problems.

There are two general approaches to installing a check valve in a reverse osmosis system. Here is a brief rundown of how that’s done.

Key Takeaways

  • One type of RO check valve connects directly to the RO membrane housing (screws into permeate water port). You might have to use Teflon tape.
  • Type B sits along the permeate water line between RO membrane and ASO valve. Cut the line and connect the valve between both ends using the quick-connect fittings.
  • Shut off the water supply first!

How to Install a Reverse Osmosis Check Valve

So, how do you install a reverse osmosis check valve?

Installing a reverse osmosis check valve is pretty simple and straightforward.

  1. Start by shutting off the water supply valve and storage tank valve.
  2. Drain any water remaining in your RO system.
  3. Then, you need to check if the valve you have connects directly to the RO membrane housing (permeate water outlet). If it does, you should find a port that you can screw the check valve into. You may need to use Teflon tape to secure the threading.
  4. If that’s not the case, and the reverse osmosis check valve doesn’t connect directly to the membrane housing, then it’s connected along the permeate water line before the ASO valve. This may require you to cut the line in two parts, connect the valve between them, and hook everything back up. You shouldn’t have to use any special fittings or connectors because most check valves connect with quick connect fittings.

Location: Where Does the RO Check Valve Go?

As mentioned before, RO check valve location depends on its type.

Type A connects directly to the permeate port of your reverse osmosis membrane housing.

Type B sits inline, between RO membrane and automatic shutoff valve.

RO check valve diagram

Other Valves Used in Home Reverse Osmosis Systems

Modern home reverse osmosis systems utilize a number of additional valves in their operation. Typically you would also have a feed valve, automatic shutoff valve, and a flow restrictor.

Feed Valve

The feed water valve simply connects your system to the water source in your home. Usually, you would have this hooked up directly to the cold water supply under your kitchen sink.

ASO Valve

An automatic shutoff valve ensures that the system doesn’t work unnecessarily once the tank is full. Without an ASO valve, or when you have one but it’s operating improperly, your system will likely keep running all the time, even when the tank has been full for hours.

Flow Restrictor

The flow restrictor connects to the drain line and limits the flow of water through it. Without a flow restrictor, most of the water that pushes against the membrane will simply flow out into the drain without getting filtered.#

It’s theoretically possible to use a reverse osmosis system in this manner, but it’s not really recommended because it will result in a lot of wasted water and reduce RO water quality.

How Under Sink RO Systems Work

An under sink reverse osmosis system is a comprehensive package for filtering household water. These systems typically work in multiple stages. First, you have a pre-filtration stage which gets rid of floating particles and chemicals like chlorine before water makes it into the reverse osmosis membrane. At that point, water is pushed against the membrane at a high level of pressure. As a result, almost only water molecules can make it through the reverse osmosis membrane.

Finally, filtered water is run through a post filtration stage to get rid of some additional contaminants like dissolved gases. At this stage, you might also add something like a remineralization filter to compensate for all of the minerals that got stripped out of the water during the reverse osmosis process.

If you have any questions about our RO check valve placement guide please don’t hesitate to leave a comment below!

About the Author Alexandra Uta

Alex is a content writer with an affinity for research and a methodical attention to detail. Since 2020, she has fully immersed herself into the home water treatment industry only to become an expert herself. Alex has been using water filters and similar products for years which has gained her lots of hands-on experience.
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