How to Service a Residential Reverse Osmosis System

Residential Reverse Osmosis System Service Guidelines

As a water treatment professional, it should be our goal to provide services that meet a certain professional standard even though profitability may be be the underlying goal. So before you rush through your next residential reverse osmosis system service call, at least make sure to follow these generally accepted service guidelines.

1. Test the untreated and treated water. It is important to test the untreated water so that you may discern the actual rejection rate of the membrane’s current performance. Just testing the treated (permeate or product) water isn’t enough data to derive the rejection rate. Replacement membranes can be an expensive component to replace so do your customer a favor and calculate the actual rejection rate. To do this, divide the treated water tds by the untreated water tds. Subtract the result from 1 and that is your current rejection rate. It is my opinion that a membrane should be changed if the rejection rate is less than 80%. of course it is ultimately up to the customer – if they are complaining about the taste of the drinking water, then you may just want to change out the membrane element.

2. Test the flow of water from the drinking water faucet – is there a strong flow or a weak flow. This will help gauge whether there is a need to add air to the bladder tank. Of course it is prudent to always drain the storage tank and check the air pre-charge but this will give you a quick visual understanding of how well the tank is dispensing water. This test will also give you an idea of the faucet handle needs an adjustment as well.

3. Change needed filters and membrane if necessary. Since there are so many types of reverse osmosis systems on the market today, it would be difficult to give one set of instructions to accomplish this task. However, some guidelines would be to wear latex gloves (you are touching surfaces that will come in contact with the drinking water), Inspect any o-rings and change where necessary. Also be sure to lube the o-rings so they remain pliable and seat well.

4. Once the filters and membrane have been replaced, and all water lines are re-connected, open the drinking water faucet and empty out the storage tank for the purposes of checking the air precharge. This is also a good practice (emptying the tank) since it provides a nice flush of the tank and it helps restore the tds of the stored water – meaning that the affect of “tds creep” may have occured over time if the tank has been used lightly (not a lot of draw down). If not much water has been drawn down over time and the tank is only refilling small amounts of dispensed water, the quality of water that enters the tank while there is a significant amount of tank back pressure is not the best possible water that the reverse osmosis can produce. if this tds creep continues, the stored water in the tank can be of poor tds quality.

5. In some cases, where bad drinking odor has been issue with your customer, you may wish to sanitize the storage tank. This is accomplished by inducing a small amount of bleach into the storage tank. The simple way to accomplish this is to assemble a jig where you have a direct feed tube from the reverse osmosis feed valve into the storage tank. The tube should be able to hold an ounce or two of bleach. Induce the bleach into the tube (via syringe). Turn on the feed vale and open the storage tank valve. Allow the tank to fill with water and allow sufficient contact time for the bleach to disinfect the tank (approx 20 to 30 minutes). Then dispense the water and refill for flushing purposes once again to ensure that no residual bleach is left in tank. The smell test for bleach is usually sufficient but a chlorine dip strip is more accurate to determine if residual bleach is still in tank. Of course tasting the water will also indicate if the tank has been properly flushed.

6. Ok, with everything reconnected and the storage tank properly pressurized (and possibly disinfected), it is time to pressurize the system and check for leaks. Leave the storage tank closed so you can check for membrane permeate production at the open drinking water faucet. It may take some time for the permeate to start flowing though. Once the permeate water is flowing from faucet, shut the faucet off and open the storage tank. It is good practice to allow the tank to fill a bit so you can check for leaks on the permeate lines.

7. Disconnect the waste water line from the drain saddle to ensure that rejection water is being made and at the right flow (visually speaking).

8. Also be sure to check the incoming household water supply for line pressure. A reverse osmosis system needs at least 40 psi to make permeate water and for safety concern…an upper pressure limit of 75 psi should be adhered to.

9. Now instruct the customer that the tank will take some time to refill with “new ” water so they should be patient. They should also dispense a good deal of the first tank of water due to non toxic membrane preservative and trapped air. Once they purge their tank once, it should be good to go for another year or so.

10. Write-up your invoice and get paid. A well performed reverse osmosis service call should provide your customer with a properly operating system that is making excellent quality drinking water while at the same time…affording you a profitable service call.

Vibrant Water Provides Reverse Osmosis System Service to All San Diego County