Approaching five years, seem to eat through carbon blocks even with regular pre filter change, pressure drop issues regularly and intermittent RR problems. Inlet sensor is reading same as external meter. Membrane change? Other suggestions? Heard that cleaning only buys you a little extra time. Seems to be our oldest two are the worst performers so...
Will have to check next time. I have little confidence in the tech I am working with when he says those are good. If he is right and both drain and product are still okay, but pressures at the carbon blocks dip under 20 psi and throw up insufficient water alarms, could this be the membrane? Or just that our block(s) are end of life? The problem is that even though they might run marginal here in our shop, up in the higher floors they fail. We try to get 6 months total out of the carbon blocks, three months in secondary and then three in primary. During the summer it was more like two to three total. When switched from secondary to primary, barely got a month on them. Is this typical? We change the 1 and 0.35 filters at least every two weeks, although I push for weekly (they're only freakin' 12 bucks each!). I am still learning the process, but too many people seem to have different opinions.
The pressure drops don't sound like they are related to the membranes, they may need changing for age or efficiency anyway if cultures or readings indicate. Your problem sounds more like the carbon blocks since that's where the pressure drop is.What's your filter delta?
Posts: 505 | Location: NYC | Registered: 04 November 2011
If product water is dropping off, membrane pressure rising, and possible bad labs, this is usually when I think about replacing membranes. 5 years is a good run if you use them frequently. Try rinsing the carbon block to drain before you send water to the RO. I know this might be a pain to do, but if in shipping the carbon blocks got dropped of rough handled, it will produce carbon fines that will give a high pressure drop.
We definitely flush the blocks to drain first and even use an inline filter pre RO. Will probably get a membrane on hand, meanwhile carbon blocks and pre filters seem to fix these issues. Every so often the rejection rate goes down, conductivity goes up. I discovered a yellow slime on the inside of the carbon block housings so we perhaps need to clean out our system a little better. Anyone else seen this?
Reading through this it seems to me that the pressure drop is being caused by a high SDI (silt density index). The higher the SDI the more large particulate matter are present (dirt). The WRO filter is typically located after the carbons to protect the RO from large carbon fines. We are all at the mercy of our municipal water supply - I have had to add a 5 micron prefilter before the carbons to make them last - not from chlorine breakthrough but Delta pressure (plugging of the carbon blocks). At one site, for about a year, I had to have that filter changed weekly.
Posts: 142 | Location: PA | Registered: 03 June 2014
I agree with EnlightenMe. I had a similar issue using a new carbon block assembly that replaced my old carbon tanks. 3 months tops and high delta across the worker block. I added another small prefilter in front of the carbons and now get 6 months before a replacement is needed. The blocks look like a filter and act like one too.
A pressure drop in pre-treatment has absolutely nothing to do with the integrity of your membrane. Insufficient water alarms are telling you the empty level sensor before the membrane is seeing air. It's kind of like assuming your car has a blown motor, when in fact it's simply out of gas.