tap water

Chlorine: Chloride is involved in the evolution of oxygen in the photosynthesis process and is essential for cell division in roots and leaves. Chlorine raises the cell osmotic pressure and affects stomata regulation and increases the hydration of plant tissue. A solution concentration of less than 140 PPM is usually safe for marijuana, but some varieties may show sensitivity when foliage turns pale green and wilts. Excessive chlorine causes leaf tips and margins to burn and leaves to turn a bronze color. Some Chloride sensitive plants may experience tip or marginal leaf burn at concentrations above 20 ppm.

Osmosis and Hard Water, Excerpted from Chapter Four, Indoor Marijuana Horticulture, The Indoor Bible:

"A small amount of chlorine, below 140 PPM, does not affect marijuana growth, but higher levels cause foliage chlorosis and stunt growth. Do not use salt-softened water. Salty, brackish and salt-softened water is detrimental to cannabis. Chlorine also tends to acidify soil after repeated applications. The best way to get chlorine out of water is to let it sit one or two days in an open container. The chlorine will evaporate (volatize) as a gas when it comes in contact with air. If chlorine noticeably alters soil pH, adjust it with a commercial "pH UP" product or hydrated lime."

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smoove said:

Here I go again...

My feeling is don't use tap water unless you know what's in it. You can request this information from your municipal water district. In fact... my water district makes their yearly water analysis report available for download directly from their website.

My water district's average ppm value for Chloride and Chlorine residual is 106ppm. Now that might seem safe... but a 100 average could also mean 50-150ppm. And that's just the tip of the ice-burg with my water. The average pH is 7.9! The average TDS (overall ppms) is 618ppm!! Some of what makes this water so hard is in fact beneficial to growing... but a LOT of it is not... So I wont use it. But... if I lived somewhere with good tap water I would.

The way I see it you have 3 options:

1. Just use your tap water and see what happens.

2. Use reverse osmosis water and forget about it.

3. Actually find out what's in your tap water, then make an informed decision on how beneficial it will be for your grow. Use it if it's good water, or find another source that's practical for your setup if it isn't.


Here's a little more info that might be helpful:


My 2cents. Hope it was helpful.

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Erysichthon said:

along with letting the chlorine evaporate you should check the ph. it may be too high or less likely too low. for soil prime ph is about 6-6.5. you can get lithmus strips or just get a pool ph kit either works, you shouldnt have to check it very often after the first check as it generally wont change that much. maybe once a week to be sure.

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