Tannins in drinking water are caused by natural decaying of organic matter. Leaves or pine needles in the gutters are generally the cause in a rainwater collection system. A faint yellowing of water generally occurs at .5 parts per million or PPMs with .5 – 2.0 PPMs looking like the color of ginger ale, and 3.0 – 5.0 PPMs would take on the appearance of dark tea. The tannins may cause a yellow color of the water, yellow staining on fixtures, and yellow staining in laundry.
Although aesthetically displeasing, tannins generally pose no real health risk, but may affect the performance of the UV system by not allowing the UV light to penetrate thoroughly through the water column.
Therefore, it is very important to minimize tannins before storage of collected rainwater. Organic matter must be kept from accumulating in gutters, down spouts, and screen baskets. Gutter screens are an effective method of prevention of organics in gutters and down spouts. Both gutter screens and screen baskets should be inspected and cleaned as needed to prevent tannins from occurring. Since the discoloration is in solution, removal can be difficult and expensive. Ozone, ion exchange, and activated carbon can help with removal of tannins to some degree. If you do end up with tannins in your water, it is best to drain the cisterns, rinse and start collection again, however the best solution is diligence in maintenance.
As the weather begins to feel more like winter than autumn and our thoughts turn towards family and friends as the Thanksgiving holiday approaches, don’t neglect your gutter maintenance routine.
No one likes to clean gutters – especially during the holiday season. But, with the winds blowing, this is the most important time of year to be on top of your gutters. Wind blows pine needles and leaves from shedding trees – not only into your yard, but into your gutters as well, causing obstructions in the gutters and downspouts. Organic matter, created by tannins in your stored water can be eliminated by removing debris from your gutters and screen baskets. While gutters should be inspected twice per month and cleaned as necessary to be sure your stored water remains clean and clear, this maintenance practice is most important at this time of year.
Don’t let an accident spoil your holidays. Please remember to take care while on a ladder by following manufacturer’s safety guidelines. To eliminate the need to climb a ladder, gutter screening is the most effective measure of first line screening. Buy good quality gutter screens for high performance. An extruded framework with stainless steel meshing is desirable.
Don’t forget the screen baskets in either the sump tank or top of cisterns, too. They should be inspected a few times per month and cleaned as needed.
These simple gutter maintenance tasks will help ensure collected water is safe and clean.