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Current IssueSeptember 04, 2015
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Ask The Expert: Extending RO membrane life
Question: Q: I'm a regular reader of WC&P magazine for the last few years and delighted to learn so much about water. Two years ago, I purchased a reverse osmosis system for my home from Culligan—model CWT35T3 Water Tower. Before buying, I told the salesperson I couldn’t feed the soft water to the towers due to a plumbing problem. He assured me that it would not make any difference except the membrane would last 6-7 years instead of 8-10 years. Water hardness is about 23 grains. A non-metallic faucet was provided with indicating light to indicate the water quality. As it turns out, the faucet was showing a green light all the time indicating good quality water until it stopped working. The new faucet Culligan installed showed a red light indicating high TDS. After changing sediment and carbon filter cartridges, the indicator turn orange for short time and then to red again indicating high TDS. A technician indicated I needed a new membrane, which is $199. My question is can hard water affect the life of a membrane? What are my other alternatives to increase membrane life?

Yashwant Mehta

Answer: A: Regarding your question concerning the effect of water hardness on RO membrane life, even with home RO units, unsoftened water will shorten the membrane life. You did not say how long the membrane lasted, but with a softener, I would expect you to get about a 5-year life on your membrane (not 8-10 years as you say was quoted to you). Let us know if you need additional information.

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