How Important is using RO filter for city water?

How important is it to use an RO filter for city water? I’m about to do my first hydro DWC grow. I have heard you absolutely have to use RO or distilled water, but other places have said it isn’t that important. Maybe I’m confusing Soil and Hydro.

My water that I buy is tested at 5 ppm and a ph of 5.5 … :+1::grin:
That’s my starting point in water in flower…
In vegg I use a ro water that is 200 ppm and a 7.5 ph …

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If you have the tools to monitor , you’ll be fine.

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Depends on your city water. My city water is over 400 ppm out of the tap, it sucks, so I use RO for my plants, myself, my pets. If you have good clean city water, it’d be fine to use. Have a TDS meter? Check your tap water.

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Just be sure to let water sit 24hrs or air bubble it for 30min per 5 gal to dissipate chlorine before use.


Thanks for the responses everyone. I have the TDS/EC Meter and a pH meter. I’ll test out some tap water. I do have an RO system on order just in case. I’m fairly certain my city’s water isn’t very clean.

My tap water has a really high PPM too. I used to buy distilled. I put in an RO system a few months ago and I love it.


Does it benefit one to check the pH and TDS straight out of the faucet and then again after 24 hours? I’ve also been curious about testing my tap water but wasn’t sure what you would need to be looking for in general. I want to say I tested mine straight from the tap and the pH was 6.something and the TDS was very low, maybe 50 or less but I’d need to do it again to be sure.

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That’s actually a good question. If you are checking tapwater, best to do it just prior to use as dissolved CO2 will lower the PH until it dissipates into the air. One thing to find out though is if your muni water supply uses chloramines. That does NOT leave water over time and requires treatment or R/O with the right filter.

I have super high water solids so forced to use R/O but with a few cautions it’s consistent. If your city water is under 200 ppm and chloramine free I’d use that.


Why don’t you run your setup by the hydro growers to make sure you’re on the right path. Tag Peachfuzz or me and we can look it over.


@Myfriendis410 I will try searching for the info on the city page and see what I can find and try calling if I have to but I am not even sure how to investigate these things lol. I know I’ve seen many people say they use tap water with no testing and works fine but I just don’t have that kinda faith in my local water :joy:

I think barring a major issue with setting up the RO system I have ordered, I’m just going to use that option. Seems like there might be too much chance for weird chemicals.


If you would like a run down of the equipment I have purchased, here you go:

VIVOSUN 2-in-1 48”x36”x72”

Main Chamber:

DWC SELF-Watering Bubbler Kit with 4 grow sites
VIVOSUN 6 Inch 440 CFM Inline Duct Fan
VIVOSUN 6 Inch Air Carbon Filter with Reversible Flange 6"x 18"
VIVOSUN 6 Inch Noise Reducer Silencer for Inline Duct Fan
VIVOSUN 6 Inch 8 Feet Black Non-Insulated Flex Air Aluminum Ducting
VIPARSPECTRA 600W LED Full Spectrum Lights with Bloom/Veg
SkyGenius Battery Operated Clip On Oscillating Desk Fan, Portable Rechargeable Mini Personal Fan
TaoTronics 4L Wi-Fi Smart Cool Mist Humidifier
VIVOSUN pH and TDS Meter

Top Secondary Chamber for Seedling/Clone Propagation:

MIXC 1020 Flat Trays with Humidity Dome Germination kit for seedlings/clones
Durolux DL822N T5 HO 2Ft 2 Fluorescent Lamp 7" wide
VIVOSUN 10"x20.75" Seedling Heat Mat and Digital Thermostat Combo Set

Bottom Secondary Chamber for Early Veg:

MAXSISUN 600W LED Grow Light, Full Spectrum LED


Rapid Rooter Plant Starters, 50 Plugs
pH Control Kit For A Balanced Nutrient Solution
Flora Grow, Bloom, Micro Combo Fertilizer set, 1 Quart (Pack of 3)
Botanicare Hydroguard Bacillus Root Inoculant, 1-Quart
HydroDynamics Clonex Rooting Gel, 100 ml
ClonexClone Solution Clone & Seedling Nutrient, Quart
Smart Power Strip Wifi Smart Plug and App Control
Apollo Horticulture Stainless Steel 1/4" Adjustable Grow Light Rope Hanger
Countertop Portable Universal 5-stage Reverse Osmosis RO Purification Water System with DI Deionizing Mixed Bed
Digital Wireless Microscope USB WiFi 50X to 1000X 8 LED Lights Compatible with iPhone, iPad, Android Smartphone, Mac, Windows

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By the way, this community is amazing. Thank you very much, sincerely.

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I’m a stoner: pictures or it didn’t happen LMAO!

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Hahahaha, Fair enough. I don’t have everything set up yet, but as soon as I do, I’ll send the pics.

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@Myfriendis410 I found this but I gotta be honest…I don’t know what I’m reading lol.


I don’t see anything to be worried about but take a sample of your water and check the TDS because I don’t see it on this chart. You still want to let stand for 24 hours or run an air stone for a few hours.

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I read somewhere that drinking ro or distilled water long term can have some negative effects. Do you need to supplement minerals you would normally get from water?


@Myfriendis410 I think I will test direct from the tap, after 24 hours and once again after nutes just to cover my bases. Maybe start on one plant and see what happens before going that route permanently. I feel like that’s a solid testing idea at least lol.