Question: Which type of flow restrictor is best for me?

Answer:

There are four types of flow restrictors being used by RO system manufacturers; 1) Inline Flow Restrictor, 2) Capillary Insert Flow Restrictor, 3) Fitting Connector Flow Restrictor Combo and 4) Integral Flow Restrictor. We will provide a brief description of each and give the strong features and weak features that each type offers.

1) Inline Flow Restrictor – The strong point for this type of flow restrictor is the ease of installation. Many of this type of restrictors have the quick connect feature built into the unit wherein the installer can merely insert the drain line into each end of the flow restrictor and you are ready to go. The two major weakness of this system are cost and lack of a check valve for safety purposes. Read about the safety features of the “combo flow restrictor” to completely understand our comments about drain line safety. The cost of an inline flow restrictor increases because this system requires three parts to be equal with one part in a “combo”. First is the inline flow restrictor, second is the fitting that is inserted into the membrane housing and then attached to the drain line tubing. The third is optional but one that we consider very important and that is a check valve to prevent drain water from flowing back into the membrane.

2) Capillary Insert – This is a small plastic piece that fits inside the drain tubing usually where the drain tubing attaches to the fitting at the drain outlet on the membrane housing. The plus for this type of flow restrictor is the cost. On the minus side, capillary inserts do not have a check valve (as noted for the inline flow restrictors) and they can be less than service friendly if you do not get the capillary to seat properly.

3) Fitting Connector Flow Restrictor Combo – This type of flow restrictor is a fitting that is inserted into the drain outlet on the membrane housing. It serves three functions. Its first function is as the connection between the RO membrane housing and the drain tubing. Secondly, it is the flow restrictor wherein it regulates the flow of water over the membrane to obtain the best performance from the membrane. Third, it is also a check valve on the drain line. The check valve safety feature is one aspect of the drain line that is overlooked by many manufacturers and RO system owners. Without a check valve in the drain line, if the drain plugs, the drain line will back up into the RO membrane and create all sorts of problems. Correspondingly, we encourage RO owners to give consideration to installing some type of check valve in the drain line for safety purposes.

4) Integral Flow Restrictor – This type of flow restrictor is made as a part of the membrane housing. Usually these flow restrictors are in an encapsulated membrane or sealed membrane housing that can not be opened. The entire housing and membrane are replaced each time. Since the housing cannot be opened the flow restrictor cannot be accessed. While more expensive each time, it is easy to change.