I replaced the membranes on our reverse osmosis unit this past weekend. When I pulled the membranes out they where solid black with carbon. We use a 5micron pre filter and it is changed monthly. Has anyone had this problem? We changed the membranes because the product had dropped overtime to less then 1gpm. The membranes were only 2 years old. I had tried cleaning them several times but had no luck. Would a 1-micron pre filter help?

when were your carbon tanks rebedded/exchanged? how often do the backflush? how often do you replace your pre filter?

We have exchange carbon tanks. not backwashable. prefilter is replaced monthly.

Who is the manufacturer of the membranes?

How many pre filters do you have?

We are going through carbon like crazy right now and we have 2 5 micron prefilters and they are catching everything. sounds like there is another problem. Has it always been like this if not there is something else wrong.

I would also check with your carbon tank supplier if they have changed to a media with smaller granule size.

How often do you clean the membranes and with what?

filmtec is the membrane mfg. We only have 1 prefilter before the ro.

I would install a second prefilter this may greatly help your problem. Good Luck

If you add a second prefilter place it in parallel to the first this will keep flow high and reduce pressure drop. Also check with the water treatment people to see if they are wetting the carbon (and possibly flushing it to drain) prior to their putting them on line. It sounds like the carbon is dry in the tank and when it is initially hit with water alot of it is being flushed downstream and overloading the prefilter.

I pretty sure they are flushing them to drain before putting them on because I have been there when they do an exchange. Could a high level of chloramines in the feed water be braking the carbon down. The chloramine level in the feed water runs very high last time I checked it it was 4.6mg/l

Is this water being pumped out of a swimming pool? 4.6 mg/L? Sounds to me like they aren't flushing the tanks long enough. I had the same problem with some of my clinics. Good luck.

Tom,

I would contact your municiple water supplier, a chloramine level of 4.6 is EXTREAMLY high!

We used to use a local Culligan distributor for exchange carbon tanks in one of our facilities and had the exact same problem. According to the information they provided us, it was the correct grade carbon but I wonder about the quality of the carbon and if they flushed them correctly. Two months after questioning them about the carbon, they sent out a letter stating that after 30 days, they will no longer service dialysis facilities (kinda makes you wonder).

We now have backwashable carbon tanks and have not had a problem since.

Chuck

I thought that was a really high level. I wasn't sure though I learn something from Chuck everytime he posts something. I would do as he suggested.

This isn't always possible because of the connector configuration, I've seen this happen when the carbon tanks are installed backwards with the flow going in wrong direction. Could a broken pipe inside the tank cause this?

Larry,

Anything is possible though I don't think this would be very likely. In the scenario you suggest, carbon granuals would definately clog the prefilter which isn't happening. This sounds more like carbon powder from either inadequate rinsing or inferior carbon.

Chuck