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RO membrane

Posted by dianeky (My Page) on
Tue, Jul 27, 10 at 13:21

When I was changing the membrane in our RO system, I dropped it on the cement floor. I inspected the outside for any damage and couldn't see any, so I rinsed it off and installed it. Now I'm wondering if there could be internal damage that would adversely affect its filtering ability. It's the type that looks like it has many concentric internal layers when looked at it end-on.


Follow-Up Postings:

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RE: RO membrane

It's most likely OK if you cleaned it and made sure nothing off the floor stuck to it and you installed it in the correct direction.


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RE: RO membrane

An RO membrane is exactly what it looks like - really no parts to be damaged by a drop. It is layers of membrane and spacer mesh wrapped around a plastic tube with holes in it. If membrane sheets are cut or punctured, or the interior tube is broken, then you have a problem, but I cannot imaging that happening with a simple drop to the floor.


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RE: RO membrane

I, too, suspect it's fine. In any event, if you have ANY RO system you should have a TDS meter. Cheap and easy evaluation of performance. Link below.

Here is a link that might be useful: TDS meter.....google for others.


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RE: RO membrane

Thank you all for your replies. Yes, I rinsed it very well (luckily I vacuumed and mopped the floor the day before), and I know I installed it correctly. And yes I will be testing the TDS. Thanks again.


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RE: RO membrane

Just thought I would post a follow-up. It appears the RO membrane is working fine, but I have questions about my softener. Water coming into the house registers 218 on the TDS meter. Post-softener-pre-RO water reads 260 on the TDS meter, while the post-RO reads 14. Why would my post-softener water have a higher TDS than the source water? I use KCl, not NaCl, for my salt. Is that the cause or do I have serious contamination in my softener?


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RE: RO membrane

Don't know, but........ my own inbound water at one location (city water) varies from 400 to 525. I've learned this is "normal" fluctuation at this location. Perhaps your location has such fluctuations, too.

I would doubt you have contamination issue short of parsing the word itself.


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RE: RO membrane

The higher the hardness of the water the more sodium or potassium ions are exchanged to soften the water. Potassium ions at about 2 to 1.

It is not uncommon for a softener to add TDS.

Everything is OK as long as the RO provides at least a 90% rejection rate.


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RE: RO membrane

justalurker: I assume what you are saying is if my pre-RO reading is 260 as it was today, then my post RO reading should be <26. And if tomorrow my pre-RO was down at 180, then my post RO should be <18?
And another question to all you knowledgable folks: the fellow who installed our softener and RO 5 years ago said that soft water was easier on the membrane than hard water, but if softening actually increases the TDS, would it not be taking a heavier toll on the membrane?
Thanks


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RE: RO membrane

If you feed an RO hard water the membrane will clog up in short order.

I have 30 gpg hard water and a 15 year old RO that has had two membranes replaced... long enough life?

Everything is working fine... enjoy your water.


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RO membrane addendum...

I have 30 gpg hard water and a softener and a 15 year old RO that has had two membranes replaced... long enough life?


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RE: RO membrane

Thanks a lot!


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RE: RO membrane

Even though a softener increases TDS it is still easier on your RO membrane. For every hardness ion (calcium or magnesium) that a softener removes, it adds two sodium or potassium ions, the reason TDS increases with a softener. While this may sound problematic at first glance, the total ions are not the only issue.

The reason softeners solve so many problems is that they remove ions with LOW solubility (ability to remain dissolved in water) and replace them with ions that have a very HIGH solubility. Since sodium and potassium dissolve so readily in water, at high concentrations, you can run them across an RO membrane nearly indefinitely without causing any buildup on the membrane. For those of us who are chemistry geeks, it is very cool chemistry. For those who do not have the chemistry/engineering mental disorder, it just plain works in your favor whether you understand it or not. Everybody is happy (love it when that happens)!


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RE: RO membrane

I'm happy...thanks!


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