rodi after filer change shows 25ppm?

[phoenix20]

So I picked up this 120g rodi unit off of ebay in december

http://www.waterfilters.net/Water-General-RO6100-Reverse-Osmosis-System_p_641-29081.html">http://www.waterfilters.net/Water-General-RO6100-Reverse-Osmosis-System_p_641-29081.html</a>

I just changed the 3 pre-filters in stage 1-3.

I measured the TDS before the filer change and got a 35 (not good).

The unit is only 6 months old.

After the filer change, I got a TDS of 23. (still not good)

What gives? Should I change the resin?

 

[seedless reefer]

After you change filters you need to flush the system for up to an hour.

 

[phoenix20]

Ah... I did not know about the flush.

I just picket up this Hanna TDS meter for $12. Figured I couldn't go wrong. Maybe this thing is worthless?

 

[down and outman]

Hanna meters are pretty good. I'd see about the flush.

 

[seedless reefer]

AND calibrate the meter!

 

[zavala83]

Always heard about the flush. It takes awhile for your filters to really kick in and start to do there job.....

 

[dannybradley]

The flush is to remove the antimicrobial substance applied to the membrane. There are two huge issues with that unit.

1. A single 120GPD membrane has a low rejection rate. 75GPD is the best flow to rejection rate ratio, at 96%. It goes downhill fast from there.

2. Horizontally oriented D.I. filters can allow water to bypass the media, or the media to settle compacted, causing the top layer of media to exhause while the bottom layer is not utilized.

 

[phoenix20]

DannyBradley;353995 wrote: The flush is to remove the antimicrobial substance applied to the membrane. There are two huge issues with that unit.

1. A single 120GPD membrane has a low rejection rate. 75GPD is the best flow to rejection rate ratio, at 96%. It goes downhill fast from there.

2. Horizontally oriented D.I. filters can allow water to bypass the media, or the media to settle compacted, causing the top layer of media to exhause while the bottom layer is not utilized.

well crud. this hobby is super complicated.

 

[dannybradley]

phoenix20;354034 wrote: well crud. this hobby is super complicated.

Yeah. I'm always learning, too. Also, take a reading after it's been running for an hour or so. Initial output is always higher than what the unit can produce. This is true at any age of the unit.

You'll still be okay with that unit. If you want to be really anal about it, change the membrane and flow restrictor out to a 75GPD or less.

 

[one dumm hikk]

phoenix20;353807 wrote: I just changed the 3 pre-filters in stage 1-3.
What gives? Should I change the resin?

If you truly only changed the first three filters, they are only sediment filters and will have absolutely no impact on TDS readings. The first three in that setup only trap/remove suspended particles, not dissolved particles. The RO membrane and DI remove the dissolved solids. You can test it on nearly any system before and after the sediment filters. You should get a slight drop but nothing major. The slight drop would be the carbon filter removing chlorine and chloramine.

What are the TDS readings before and after your RO membrane?
And what is the TDS reading before and after your DI resin?

Take the clip that holds two DI resin chambers to the RO membrane housing off. Turn the DI chambers vertical and it will help tremendously in stopping channeling. When you turn the DI vertical, make SURE the water from the RO membrane comes in the bottom and exits the top.

 

[phoenix20]

Awesome! Thanks guys. It ended up being the flush. After about an hour of running, i'm getting 3 TDS now.

Thanks for the helpful info!

 

[buckeye field supply]

phoenix20;353807 wrote: So I picked up this 120g rodi unit off of ebay in december

http://www.waterfilters.net/Water-General-RO6100-Reverse-Osmosis-System_p_641-29081.html">http://www.waterfilters.net/Water-General-RO6100-Reverse-Osmosis-System_p_641-29081.html</a>

I just changed the 3 pre-filters in stage 1-3.

I measured the TDS before the filer change and got a 35 (not good).

The unit is only 6 months old.

After the filer change, I got a TDS of 23. (still not good)

What gives? Should I change the resin?[/QUOTE]

A few comments on what you bought:

Your filter stages go like this:
Stage 1: 5 mic sediment filter (if you don't have trouble with heavy sediment loads, replace this with a 1 micron depth filter next time)

Stage 2: Granular Activated Carbon. This type of filter has no place in the high capacity systems we use in this hobby. These filters are a hold-ove from the days when RO's were only used for drinking water and had very low capacity membranes (e.g., 12 gpd). When you change your filters next time don't replace it with GAC - instead use a carbon block.

Stage 3: 0.5 mic carbon block. This is a good carbon block, however, your system doesn't have the correct filters in front of it, so this filter too is out of place. Additionally, in normal situations you don't need 2 carbon prefilters.

Stage 4: 100 gpd membrane rated at 65 psi and 77 degree water. Not sure why you mentioned "120 gpd"?

Stage 5 and 6: I couldn't tell from the website if these were both DI, or one was DI and one was GAC ("taste and odor filter"). These ebay systems are often misconfigured so that they have GAC after the DI. If that is the case, you'll never see 0 tds, and the gac stage should be removed. The water is as clean as the system can make it after it comes out of the DI stage.

Remember - no metal contact for DI water - so don't send DI water to a pressurized storage tank.

Regardless of the number of DI stages you have, unclip them and orient them vertically with bottom up flow. These ebay outfits retrofit drinking water systems and sell them into this hobby. Those horizontal housings are intended for GAC - not DI resin.

What is your current tds reading at:
Tap?
RO?
DI?

Russ @
Buckeye Field Supply

 

[buckeye field supply]

phoenix20;354034 wrote: well crud. this hobby is super complicated.

And in this case it really doesn't need to be. Stick with a vendor who specialises in water purification systems for this hobby and you'll have a much better chance of getting a system and replacement filters that are appropriate.

Ebay is cheap, but as you're seeing, not always the best value.


One more thing - I noticed that system doesn't have a pressure gauge. This is an important tool so you'll know if you have enough pressure to run the system, and if you do, it will tell you when/if your sediment filter and carbon filters are clogging/clogged.

A pressure gauge add on kit is inexpensive, and would be an important addition to that system.

Russ @
Buckeye Field Supply