[snowkitty]

About six months ago, I invested in an RO system to treat my tap water. My final selection was the Hydrologic Stealth RO 200. My personal problem was maintaining a steady ppm when using an AN feeding schedule. The RO water helped a lot with maintaining ppm and healthy plants. My tap water tests between 300-400 ppm and I know that my community buys from two different adjacent water sources, so my tap water is not consistent. I get 0-10 ppm after running my tap water through the Hydrologic.

A rule of thumb is that if your tap water tests over 300 ppm, you should look to alternate sources or water treatment. Here’s some of the research that went into my RO decision:

Why (or why not) RO?
RO Pros
* Excessively high levels of minerals in your water causes nutrient lock out. High levels of calcium locks out magnesium & phosphorus. If you have high ppm in your tap water, your choices are (1) installing a RO system, (2) collecting rainwater, or (3) buying distilled water.
* You are going to get a more accurate ppm reading after you add your nutrients if you start with RO or distilled water that has a near-zero ppm to begin with.
* As you add RO water to your rez, the pH is going to remain stable overall instead of fluctuating based on the contents of your tap water.

RO Cons
* Cannabis plants consume high levels of Calcium and Magnesium so when you take it out of your tap water, it is going to have to be added back in your overall feeding plan. If you have decent tap water (without excessive levels of Ca, Mg, or others) than installing RO is overkill that you are going to have to compensate for later.
* RO water requires Ca/Mg micronutrients to be added back. You can do this by mixing tap water with your RO water (this solution is free but I am not sure how to dial in the right levels and I think you'd want to let the water sit so any chlorine evaporated off). Or you can purchase Cal Mag, Sensi Cal, Earth Juice, etc.
* RO systems generate an incredible amount of waste water. People have reported using 4 gallons of regular water to generate 1 gallon of RO water. Another statistic is that RO systems have a 5-15% recovery rate and the rest of your water goes down a drain.
* If you have a holding tank for your RO water, you can get bacterial growth. Someone reported brown algae if exposed to light.
* Faucet-mounted systems can be slow.
* For the purposes of gardening, we’re only concerned with the removal of excessive nutrient levels, and most RO systems focus on the removal of pathogens that aren’t an issue in gardening. So you might be paying for a lot more than you need when you could use a whole-house filter to target Ca/Mg hard water removal.

RO membranes
There are two common household RO membranes: Thin Film Composite (TFC/TFM) and Cellulose Triacetate (CTA). TFC/TFM is non-chlorine tolerant (must use a carbon pre-treatment), less susceptible to fouling from bacteria, and rejects 98% of standard contaminants. CTA is chlorine tolerant, more susceptible to fouling from bacteria, and rejects 93% of standard contaminants.

RO Product Comparisons
Choices for RO systems include hydroshop systems, aquarium systems, whole house systems, and ebay systems. Here are some of the main ones I found in my search:

HydroLogic: StealthRO200
$300-315
200 gallons/day
98% contaminant removal
4-Stage: Carbon pre-filter, sediment filter, 2 RO membranes
Garden hose connector & inline shut-off
8’ RO Line, 4’ Feed Line, 8’ Drain Line
Optional: float valve, extra tubing, under sink connector

SpectraPure: Eliminator 200 gpd
$299.95
200 gallons/day
Garden hose adaptor
3-Stage: Sediment filter, carbon filter, RO membrane
SpectraPure replacement filters ~20% more expensive than Hydrologic .

eBay – filterdirect: Residential RO System R05
75-85 gallons/day
$135
98% contaminant removal
5-Stage: Sediment filter, 2 carbon pre-filters, RO membrane, final inline carbon filter
Long reach faucet, pressure gauge, storage tank, shut-off valve, membrane flush feature

thefilterguys.biz: Ocean Reef Miser Six Stage RO/DI 150 GPD
$265
150 gallons/day
98% contaminant removal
6-Stage: Sediment filter, 2 carbon filters, 2 75 GPD membranes, DI housing
Garden hose adaptor, pressure gauge, drain connection
These guys do custom units so you could probably ask for one without the DI cartridge.

Air Water & Ice: The Cube RO/DI
$239.95
150 gallons/day
98% contaminant removal
6-Stage: Sediment filter, 2 carbon filters, 2 TFC 75 GPD RO membranes, DI cartridge
Choice of hose, faucet, or supply valve connection
Comes with 2 75gpd membranes which have a 98% rejection rate. For the same price you can request 100gpd membranes but those only have a 90% rejection rate.
These guys do custom units so you could probably ask for one without the DI cartridge.

Air Water & Ice: G.E. Merlin
$499.95 incl. extra filters
700-1100 gallons/day
Tubing for all connections, automatic shut-off, drain saddle
3-stage: carbon pre-filter, 2 TFC membranes, carbon post-filter
This is the time tested system for whole house RO or if you want to open up a pet shop water supply. Lots of data and field expertise available on this one.

HydroLogic: Merlin Garden Pro High-Flow
$589.95
750 gallons/day
30 gallons/hour
95% contaminant removal
3-Stage: Carbon pre-filter and 2 RO membanes
Garden hose connector & 3.8” inline shut-off
12.5’ RO line, 4.5’ Feed Line, 4.5’ Drain Line

I know Whirlpool also has a system on the market but I had narrowed my search by then so I didn't look up the specifics...

[Lost]

I got one off of ebay.. 0-10 ppm for 100 bucks.. Can't beat that.. Ill probablly buy another one in a year or so rather than replace the filters, lol..

[Smokin]

Great job researching snowkitty! My next investment and totally trusting your judgment.

another downside is the waste water generated is toxic...

Originally Posted by snowkitty

* For the purposes of gardening, we’re only concerned with the removal of excessive nutrient levels, and most RO systems focus on the removal of pathogens that aren’t an issue in gardening. So you might be paying for a lot more than you need when you could use a whole-house filter to target Ca/Mg hard water removal.

for those 2 reasons I now just use a 2 stage filter to clear up my well water - for the garden that is - still use RO for drinking water...

[Jalisco Kid]

I bought my merlin for 315 on the net. JK

[budfarmer]

Hey Rolln J what type of filters are you using ? Do they drop the PPM or just take out sediment?

I think its a whirlpool - it drops ppm from 450 to about 200. I got it at lowes for like 60 bux - replacement filters are 30...

[true grit]

I picked up a Hydrologic100 for $129.99 at the local store...seen em go for as much 149.99. Filters well, I can fill a 5 gal bucket in about 45min-1hr and PPM is around 10-12pmm.

[SimplyGreen]

I'm not a spammer but I'm cheap and purewaterclub.com has better prices than anything posted here. I don't have mine yet (waiting on delivery) but I was recommended to them by another grower who's using their 300gpd unit.

[strainman]

Yo True whats the set up like, does its just connect under the sink? Bout to cop the stealth 100 too since the RO filter I have now is mad slow and only gives me like a gallon every couple hours!