RO Filter Options

havnfun328

havnfun328

AC Members
Sep 11, 2006
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Kansas
I'm ready to by an RO unit (tired of trucking to Walmart to buy water), and I'm wondering if it makes much difference what I buy. Is a typical undersink unit ok? Such as

http://www.lowes.com/lowes/lkn?action=productDetail&productId=129808-43353-WHER25&lpage=none

Or does it need to be desgned for aquariums, such as:

http://www.drsfostersmith.com/Product/Prod_Display.cfm?pcatid=4459&N=2004+113775

I'd like to use an undersink unit so I can use it for drinking too, but if it's not good enough for the tank then I need to reconsider.
 
Yes, what you buy in a RO/DI unit does make a difference. The best performing units come with a DOW Filmtec 75gpd RO membrane, 10" vertical pre-filter cartridges (standard size), and a 10" vertical DI resin chamber. In getting a unit that uses the standard 10" cartridges, you are not limited to a particular manufacturer's selection of cartridges and can customize the pre-filter array to best suit your needs. You may want to add a pressure gauge (after the pre-filters but before the RO membrane) to monitor pre-filter life (as the pre-filters clog, the pressure to the RO membrane will drop noticably). It's good to have a TDS meter to go along with your RO/DI unit -- the stick style meters are fine and easier to maintain, but there are TDS meters that install in-line on a RO/DI unit to monitor TDS levels.

Do you have well water or city water? If city water, does it contain chloramines? Do you have good water pressure? If not, you'll likely need a booster pump to create / maintain optimal water pressure to waste less water and improve the efficiency of your RO/DI unit. The answers to these questions will influence your choice and the final cost of a RO/DI unit.

Check out some of the RO/DI units on these sites...
thefilterguys.biz (very nice, bought from them, use their own products, will help you choose or even customize a unit to fit your needs)
buckeyefieldsupply.com (heard very good things about their customer service)
purelyh2o.com
airwaterice.com (a popular choice on many discussion boards)
spectrapure.com (pricey, but what are considered some of the best RO/DI units available)
Most are less expensive and will do much more for you than either of the units you linked to.

In reality, any RO/DI unit can be used in an undersink application. It's all a matter of how you want to hook it up (there are a few different ways to connect one to your water supply) and where it's most conveniently placed. Also, any aquarium quality RO/DI unit can be used to make drinking water. It simply requires installing a T in the line that leads from the RO membrane output to the DI chamber and connecting the T'd line to a pressure tank (otherwise you'll wait forever to fill a glass of water). You really don't want to drink the water after it goes through the DI resin.
 
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I have city water with good pressure (should be >60psi). What is TDS? Total Dissolved Solids?

I wasn't planning to get a DI unit, just RO. Most of the household RO units i've seen have an indicator light on the dispenser for filter status.

I'd like to keep the price down to around $200, but do want to do right for my tank.
 
I have one on order that should be here any day. Mine is going to be for drinking as well. A priority for me, was to have a water tank large enough to replenish the water fast enough.

For instance, my brother has the RO unit and would like to use it for his water changes. His is located under his kitchen sink so his water tank is small. For him to do a water change on his 60G, would take a LONG time- the tank only stores so much (2 gallons I think), and then he has to wait for it to replenish.

Since my tanks are larger, my water changes usually involve changing 25% of the water which is either 25 or 37 gallons. Because of these amounts of water I have to change, I chose to go with a 40-gallon RO tank. With replenishment, it will go up to around 75 gallons a day. This, of course, will not fit under my kitchen sink. But it's going to have a drinking line that goes there. With the larger water tank, although more money, I don't have to use 2 gallons, wait, use 2 gallons, wait, etc.

So if this is important to you, I'd recommend a larger tank. I see you have a 90gal so you may want to look into this.

Because of the answers I received in this thread...

http://www.aquariacentral.com/forums/showthread.php?t=94175

I chose for the larger, more convenient size (for me).
 
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I have three 5 gal jugs that I have been using when I buy water. I can fill these at my leisure (more or less) so a 25 gpd filter should be good enough. I also plan to mount the tank in the basement, so I should have room for a decent size.
 
You'll pay almost the same for a unit with a 25gpd membrane as one with a 75gpd membrane. That rating is under optimal conditions -- if the temp or pressure (or both) is low, it'll produce at slower rate.

Yes, TDS = Total Dissolved Solids. RO alone will not create 0 - 1 TDS water, unless your source water has incredibly low TDS to begin with. There are still ions that pass through the membrane, such as some of the nutrients, which are things we don't want to build up in our tank. This is why the DI part becomes important.

What are the indicator lights indicating? Low pressure, high TDS, etc.? I'm skeptical whether or not they are sensitive enough to monitor water quality on a level desirable for reef tank use.

There are plenty of RO or RO/DI units designed for reef use that are well under $200. You should be able to add a small drinking water tank and still stay under $200.
 
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