In some areas of the country, tap water can be filled with minerals such as calcium and magnesium that can cause it to be more alkaline. This water, which is sometimes known as hard water, can affect plants negatively if it is used to water them. Over time the minerals in the water can build up in the plant's soil and eventually burn the plants, causing brown tips and stunting plant growth.
Select a reverse osmosis filter that was created for gardening applications. Unlike under-the-sink models of reverse osmosis filters, the gardening reverse osmosis filter has garden hose fittings and requires no installation. You can purchase a gardening reverse osmosis filter from a hydroponics supply store.
Attach the reverse osmosis filter to a standard garden hose by screwing the hose onto the intake valve of the filter with the hose attachment.
Turn on the garden hose at the tap.
Allow the filtered water to run from the reverse osmosis system into a watering can. The water will be pushed through the filter by more water as you run your garden hose.
Water the plants by tipping purified water into the top of the plant containers until the soil is saturated.