" How Tap Water Can Impact Indoor Growing | Herbal House

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How Tap Water Can Impact Indoor Growing.

Tap water, especially when not distilled or filtered contains several things that are not ideal for your plants 

These things can be, but are not subject to, lead, chlorine and pathogens. In this blog post we will describe the different things to look out for and some simple solutions to make sure you are giving your plants the best water they can have.

Water temperature and plants 

Using tap water fresh out of the tap does not guarantee it is good quality for your plants. The temperature of the water will change depending on the day. The hardness and pH will also differ depending on your region.
Plants such as tropical plants are very sensitive to sudden changes in temperatures and giving them water out of their ideal temperature range would most definitely lead to the plants being shocked.

Reason for mixed Chlorine with water 

Most municipalities add Chlorine as a gas, but when the Chlorines forms are mixed with water, hypochlorous acid (HOCl) is produced, which is what does the disinfecting making it safe for us, humans, to drink.

How to make the plants healthy 

Get rid of Chlorine

Getting rid of Chlorine is very important for your plant health, however, as Chlorine will kill of your precious microbes that your plant needs to live a happy life. This is incredibly important for organic growers as they rely on high microbial activity within their growing medium to keep their plants happy.
Letting the water sit in your watering can or bucket for a day will ensure that there is adequate time for the Chlorine to dissipate. However, this is dependent on a few key variables such as, the water and surrounding air temperatures, the pH of the water, the amount of surface area of water that is exposed to air and of course, the Chlorine content of your tap water as this changes depending on recent storms etc in your area. Actively aerating your water via a pump and air stones will enable you to get rid of the chlorine much quicker, anywhere from 20 minutes to 4 hours.

Use pH adjusting solutions based on the area you live

The amount of chemicals or the hardness of your water can differ in dependence on your living area. If your water is too hard, then it can bring on a lot of downsides. Auckland water, for example, is quite hard compared to other regions and because of this the pH tends to come out much higher due to the increased amounts of Magnesium(Mg) and Calcium(Ca). People in these regions will need to take more care when feeding your plants tap water from these regions.

A water pH level that is too high means certain nutrients will be unavailable to your plant. It is common for people to use pH adjusting solutions to get to their desired pH range required by their plant.
Another common issue arises when doing so. If using Phosphoric acid when adjusting a water solution, especially before any other nutrients are added. Carbonates will form into phosphates, one in particular, Calcium Carbonate(CaCO3/Limescale) this causes major issues especially when used in a hydroponic setting as this will cause blocked lines. To negate this issue, using a pH down that uses Nitric acid instead, will ensure there is no build up in peoples systems.

Pros and cons for reverse osmosis system 

The best thing you can do is to implement a Reverse Osmosis Filter into your growing situation


Although these won't remove Chlorine, a Reverse Osmosis system will remove all minerals and contaminants from the water. If adding nutrients to your water, this will allow you to control the nutrient levels with absolute precision giving your plants exactly what they need.


The downside to using a Reverse Osmosis system is that they require a fair bit of maintenance. We would suggest to seriously consider a RO filter if your tap water supply shows 300 PPM or higher.