Growmax Power Grow 500 - 500 Litres/Day Reverse Osmosis System
Best for: Growers with one or two reservoirs who want genuinely low-EC water without paying for more output than they'll ever use.
Our thoughts
This is the entry point into GrowMax's actual RO range, as opposed to their carbon filters - and for most single or twin-reservoir setups, 500 litres a day is plenty. It's not trying to be a commercial unit, and it's priced accordingly. If you outgrow it later, the Mega Grow 1000 is the natural next step up.
The GrowMax Power Grow 500 is a 3-stage reverse osmosis system producing up to 500 litres of pure water a day (around 150 gallons/day on the membrane's rated output). Water is pushed through a 5-micron MaxPur sediment pre-filter, a CleanGreen carbon block to remove chlorine and organic contaminants, and then a high-flow 150 GPD membrane that rejects up to 95% of dissolved salts and heavy metals along with up to 99.9% of chlorine. A built-in pressure gauge lets you check the unit is getting at least the 40 PSI minimum it needs to work properly, ideally 60 PSI or more for best performance.
The housings use double O-ring seals to keep everything watertight, and are UV-safe and opaque to stop algae or bacteria growth inside the unit - a small but genuinely useful detail for a filter that's often left plumbed in and running for months at a time. GrowMax also sell a four-stage version of the Power Grow 500 with an added deionisation cartridge, which strips out the last of the remaining EC/TDS if you need water that's about as close to pure as it gets.
How it compares
It's the smallest true RO system in GrowMax's line-up, distinct from their carbon-only filters (Eco Grow 240, Garden Grow 480, Pro Grow 2000) which don't touch dissolved salts at all.
- At 500 litres/day it's half the output of the Mega Grow 1000 and roughly a sixth of the Pro 3000 - the right size if you're filling one or two reservoirs rather than several.
- Against HydroLogic's MicRO 75 (around 280 litres/day) it produces noticeably more, while sitting below HydroLogic's Stealth-RO150 (around 560 litres/day) - a fair mid-pack entry-level RO unit.
- The optional 4-stage deionisation upgrade puts it in a different league to basic carbon filters, since it's removing dissolved minerals rather than just chlorine and sediment.
For most home growers, this is the smallest unit that actually does what people mean when they ask for "an RO system" - genuinely low-EC water, not just dechlorinated tap water.
Usage guidance
A straightforward plumb-in job once you've checked your mains pressure.
Installation
Connect to a mains cold water supply, fit the shut-off valve, and route the purified line to your reservoir with the waste line to drain. Check the pressure gauge reads at least 40 PSI once running.
Filter changes
The CleanGreen carbon block and MaxPur sediment filter are both designed for easy replacement - swap them on a set schedule rather than waiting for a visible drop in output.
Stepping up to deionisation
If your feeding programme needs water that's essentially at 0 EC, look at the 4-stage version with the deionisation cartridge rather than trying to push the standard 3-stage unit further than it's built for.
Technical specifications
- Output: up to 500 litres/day (approx. 150 GPD)
- Stages: 3-stage (sediment, carbon block, RO membrane); 4-stage with optional deionisation cartridge
- Salt/heavy metal reduction: up to 95%
- Chlorine reduction: up to 99.9%
- Sediment pre-filter rating: 5 micron (MaxPur)
- Minimum operating pressure: 40 PSI (60+ PSI optimal)
- Housing seals: double O-ring, UV-safe opaque casing
- Included: pressure gauge, CleanGreen carbon block, MaxPur sediment filter, RO membrane, tubing, shut-off valve
Who this is for
- Growers with one or two reservoirs who need low-EC water without commercial-scale output
- New RO buyers who don't yet know if they'll need more capacity down the line
- Growers wanting the option to add deionisation later without replacing the whole unit
- Anyone currently mixing nutrients into untreated hard tap water and fighting EC drift as a result
Our take
The Power Grow 500 is a proper 3-stage RO system at a size that suits most home grows - not a compromise, just correctly scaled. It does the fundamental job of an RO unit (real EC reduction, not just dechlorination) without asking you to pay for output you won't use.
Does exactly what it should, day in, day out. A sensible starting point if you're moving to RO for the first time.
