When we water the garden from our water tank there’s a strong sulphur (rotten eggs) smell. Obviously we don’t drink the water, it’s just for the garden, but is there anything we can do?
Welcome to the Bunnings Workshop community @Shane . It's fantastic to have you join us and many thanks for your question.
There are several causes for the smell to occur in your water tank.
- Sludge and soil contamination at the bottom of your tank
- Poor aeration of the water tank causing anaerobic conditions
If leaves, soil and debris are gathering in your gutter and flowing in to the tank and dropping to the bottom, you might have to clean it out with a pool leaf scoop and clean the bottom of the water tank as best you can. Most folks chlorine bomb their tanks to kill off the bacteria in the tank and take the smell out as well, however this particular method is not good for your plants if you are using the water to irrigate them. Plus the chlorine in the water will damage the finish on your cars and furniture should you decide to use this water to clean them. My best recommendation is to use an earth friendly rain tank purifier. There are currently dozens to choose from but our main objective is to look for the one that has the longest effect.
If the water in the tank is sealed and stays stagnant or is still for more than three months, that is enough time to produce anaerobic conditions. Simply topping up the tank with your garden hose and letting the tank overflow a bit is enough to introduce oxygen back in to the water. Thereby eliminating the possibility for poor oxygen conditions. Open the top of your water tank to let it air out is also a good strategy.
If the smell persists then perhaps its time to use a more potent solution such as chlorine. However please be aware of the effect it could have on all your plants and other items that you may may wish to use this water on. Chlorine eventually evaporates from water but it has to be exposed to the sun. Keeping your tank open to the air and letting sunlight in and topping up the water will speed up the process. By my estimates chlorine will stay in the water for at least 30 to 40 days in a 5000 liter tank if left undisturbed. Please update us on what steps you've decided to take to help our members who are in the same situation. Good luck and stay safe.
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It's great to see you've already received a helpful reply from the knowledgeable @redracer01.
Can I ask if you have a first flush diverter on your system? They prevent sediment, bird droppings, spiders, insects, mosquito eggs and debris from entering the rainwater tank. When this organic matter breaks down within the tank, it creates the sulphur smell.
Many rainwater tanks are fitted with a Rain Harvesting 400mm Tank Screen. Do you have a screen and have you checked to see if it is filled with debris?
If your water is passing straight from your gutters and into the tank, I would suggest the first thing to do is install a first flush diverter and/or a screen. For a D.I.Y. installation, you might find a Rain Harvesting 90mm Leaf Eater Original Rain Head to be useful.
We look forward to you solving this issue and encourage you to let us know if you need further assistance or have questions.
Thank you. We do have a screen but perhaps I’m not diligent enough with cleaning it out. Will try putting some tap water into it.
This is the only opening. So I should unscrew this screen and leave it open for a few days?
That's the one @Shane. I'd recommend leaving it open for the best part of a week.