ro/di ammonia

[nicko1]

I have the USA 110GPD RO+DI REVERSE OSMOSIS WATER FILTER made by Water General I installed it a few years ago. The problem I have is a consistent ammonia reading of 0.25 to 0.50 from the ro/di unit, my reef tank reads at 0.25. I recently changed all filters and resin and still have same readings. Do most people just treat water with Amquel or other products or is there a better way? THANK YOU IN ADVANCE for any replies.

[AZDesertRat]

There are several issues here. All have to do with your RO unit.
It sounds like you local water utility uses chloramines for residual disinfection. Chloramines are chlorine and ammonia combined.
1. To help combat this you need to use much better carbon filters than the WG units come with. There are two carbon filters that are effective at reducing/removing chloramines. One is a granular activated carbon cartridge. This is a special carbon unlike the normal GAC or large micron carbon blocks that come standard equipment. The other and the one I prefer is a Matrix brand Chlorine Guzzler solid carbon block in the 0.5 micron variety. It has more surface area pores than granular and does not break down and form fines or dust which can foul a membrane if you do not follow a granular cartridge with an additional prefilter or low micron carbon block.
2. The membranes tha came in the supposed 110 GPD units are normally a 100 GPD, 90% efficient nanofilter and not a true 98% efficient RO membrane. Nanofilters are not even NSF/ANSI certified for drinking water, they are listed as "Pool and Spa Use" according to their NSF label. What this means is they are poor performers when it comes to nitrates or ammonia. Even a good RO membrane is only 90% effective at nitrates so a nanofilter is much less efficient. I would recommend replacing your membrane with a Dow Filmtec 75 GPD one. Much more efficient and really about the same GPD. WG says 110 GPD which not one membrane manufacturer builds. Its a made up number arrived at by inflating the pressure numbers to 65 psi or higher. In fact a 75 GPD Dow will produce 75 GPD at 50 psi and 90 GPD at 65 psi.
3. The third part of this is the DI. WG units use a very poor design for the DI chambers. To get effective treatment you really need a standard sized 10" vertical canister which has at least two advantages. One is it holds much more DI resin, 20 oz in fact. The other is they have a bottom up flow pattern so all water and resin come into contact with each other. In a small horizontal tube you do not have as much resin to begin with than you can get short circuiting or channelling in the tube so water bypasses and does not get treated fully.

It takes all three components to work effectively, one or the other will not do it alone. Good carbon block, good membrane and good DI. Unfortunately most drinking water systems are just that and are not suited for reef quality water without major modifications and cost.

[nicko1]

Thank You AZDesertRat for your very informative response I will replace filters or buy new unit. What can I do until these changes are made, use Amquel Plus, buy water, something else?