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Is Your Water Hurting Your Yields?

Is Your Water Hurting Your Yields?

Alex Grady

Unfiltered water's full of impurities. Left untreated it'll slow plant growth and damage your grow room equipment.

So what's in your water?

Find out more - Take a look at our infographic!

RO Water

Picking a Filter

For best results, use an RO filter!

Our GrowMax Reverse Osmosis Filters remove up to:

  • 99% of chlorine
  • Reduce sediments to 5 microns
  • 95% of salts & heavy metals

All GrowMax filters are easy to connect - you can use them right out of the box!

If buying an RO Filter, make sure it produces enough water:

Pure Water Produced
Power Grow 500 up to 500 litres of pure water a day (20 litres an hour)
Mega Grow 1000 up to 1000 litres of pure water a day (40 litres an hour)
GrowMax 3000 up to 3000 litres of pure water a day (125 litres an hour)

Feeding with RO Water

To prevent pH problems when using RO Water in your feed, make sure that you:

in DWC / NFT

1) Add 0.5ml - 1ml of SHOGUN Silicon per L of RO

2) Adjust your pH to neutral

3) Add CalMag until your nutrient strength is 0.2 EC - 0.4 EC

4) Mix your nutrients as normal (use soft water formulations)

coco / rockwool

1) Add 0.25ml - 0.5ml of SHOGUN Silicon per L of RO 

2) Adjust your pH to neutral

3) Add CalMag until your nutrient strength is 0.2 EC

4) Mix your nutrients as normal

in soil / pure organics

You can irrigate using straight RO water as there are already carbonate buffers in soil.


If you're not using a dripper or recirculating system, keep your nutrient moving with a water pump. Since there are no chloramines or chlorides in your water, it'll stagnate if left still for 5 days or more.

*When adjusting your pH, mix 1ml of pH down with 1L of RO water. Add 20ml of this mixture at a time to bring your pH down.

What Next?

Here are a few extras you may need.

green booster pump

Grab a Booster Pump (if needed)

Reverse Osmosis filters need a water pressure of at least 40 PSI.

Tap water pressure varies, so you may need a booster pump – it’ll raise the pressure in your RO system by an extra 15-50 PSI (dependent on tap water quality and RO capacity).

For best results, aim for 60 – 80 PSI. With this pressure you'll get a better pure water to waste water ratio.

green carbon block filter

Keep spare Filters

You'll want to keep a carbon filter and sediment filter handy. Change them every 3 months to preserve the life of the RO membrane in your RO filter.

Silver Bullet Roots

Keep it Sterile (hydro)

In a hydro system, use Silver Bullet Roots. Nothing else is as good as this stuff.

It'll kill 99.99% of all root nasties, including Pythium.

Roots inoculated with Mycorrhizal Fungi

Add beneficials (media)

With impurities gone, there's nothing left to restrict microbial activity. All the biological stimulants you know and love really come into their own.

We're talking about the likes of Charge, Biosys, Mykos & Mammoth P.

The Facts

green booster pump

What are the signs of hard water?

Limescale at the end of your tap and on the inside of your kettle.

Does hard water affect grow lights?

You lose 10% of reflectivity over 3 months, due to mineral deposits on your lamp and reflector, if you use it with a humidifier.

Does hard water damage carbon filters?

Yes, unfiltered water clogs up filters, causing limited odour control and poor extraction while shortening your filter's life if you use it with a humidifier.

How do you test for hard water?

Use a CF meter: 0 - 3 CF (soft to moderately soft), 4 - 5 CF (medium to moderately hard) or 6+ CF (hard to very hard).

How do you remove water contaminants?

With an RO (reverse osmosis) Filter.

What does an RO filter remove?

CAC03 (Calcium Carbonate), MgC03 (Magnesium Carbonate) and Cl (Chlorine).

How easy are RO filters to use?

Very easy - you can connect them to a tap or pipe.

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