Tds

[Hitsnorth]

I havent changed my membrane or filters in my RO unit in well over 2 years. Today I checked the TDS of my tap and it was 53 and coming out of my RO it was 3. I dont even have a DI on my unit. Should I really be concerned about 3 enough to add a DI to the end? Should I change my membrane if its still getting me from 53 to 3 tds?

 

[ShaunW]

That's a tough one! The 3 TDS could be just standard error on the measurement. However, I am a firm believer of a 0 TDS reading. If it was me I would add a DI (it's not that expensive, for piece of mind), and or change the RO membrane.

Do you have good pressure over the membrane, because if you don't it may not be working to its full capacity.

 

[Deanos]

Keep in mind R/O only filters will not remove all TDS. Some are good for 95%, while others are rated at 99% removal rate. If your unit ever gave you 0 TDS, it was due to a combination of the sediment AND R/O filters.

 

[jhale]

the DI of course will knock it down to 0, do you need it? I always like starting with 0 for my topoff and make up water.

what's in your water?

 

[alrha]

0 is less than 3. what have you got to lose but unwanted stuff (and $).

 

[jackson6745]

I read somewhere that a DI will effect the reading of your TDS meter and give you a 0 reading when actually the water is way more than 0 tds. I tested this on an old tap water filter (aquarium pharmaceuticals) and I got a 0 tds reading.

 

[alrha]

???
why cant it be just due to the fact that the DI removed the DS?

 

[Unresistible Blue]

I havent changed my membrane or filters in my RO unit in well over 2 years. Today I checked the TDS of my tap and it was 53 and coming out of my RO it was 3. I dont even have a DI on my unit. Should I really be concerned about 3 enough to add a DI to the end? Should I change my membrane if its still getting me from 53 to 3 tds?

How much have you been using your system? If its a lot, I suspect you need some new prefilters.

If its just a little, I'd be concerned about biofouling of the filters.

Here's what I suggest. Check your pressure gauge to see if one or both of the prefilters (sediment filter, carbon block) are clogged. Inspect each one - look for obvious signs of clogging and smell each one for signs of biofouling indicated by a bad oder.

Put pencil to paper and calculate the amount of permeate and waste water you've run through the system in the last two years and compare that to the chlorine capacity of the carbon block. If you are within 30% of the capacity, or if you don't know the chlorine capacoity of the block - replace it.

If you have GAC rather than a block, pitch the GAC and get a block.

Your membrane is rejecting about 94% of the total dissolved solids presented to it. What brand name of filter do you have, and what is its gpd capacity? What is your tap water pressure? It may be that you need a new membrane and you may not. Like the prefilters, pull the membrane out and inspect it. Look in the RO housing for a build up of "crud" that may need to be cleaned out. Squeeze the membrane (best to use sterile rubber gloves) - does it sound like it has sand in it? Smell the ends of the membrane - any sign of biofouling?

Blue