A backyard waterfall is both relaxing and invigorating. The sound of rushing water rolling over the rocks has an almost magical calming effect. As the water cascades over the swimming pool waterfall into the body of water it’s a beautiful scene. Maintaining the clarity of the water is simple if you follow some basic water chemistry principles.
The water balancing in your backyard waterfall is not a very complicated exercise. It is simply the relationship between different chemical measurements in your backyard waterfall water. The water is always changing, year round. Snow and rain affect the water balance - in short, anything that comes in contact with the backyard waterfall.
Water that is "balanced" has proper levels of pH, Total Alkalinity, and Calcium Hardness. It may also be defined as water that is neither corrosive or scaling. This concept of water balance is derived from the fact that water will dissolve and hold minerals until it becomes saturated and cannot hold any more water in solution.
When water is considerably less than saturated it is said to be in a corrosive or aggressive condition. When water is over saturated and can no longer hold the minerals in solution it is in a scaling condition. So then, balanced water is that which is neither over nor under-saturated. Here are some definitions of the three keys to proper water balance.
pH is a measure of how acidic or basic the water is. pH is a logarithmic scale from 0-14, with 7 being neutral. Below 7.0 and a substance is defined as being acidic, while levels above 7 are said to be basic or alkaline. Everything that enters a backyard waterfall has a pH value. Ever heard of acid rain? This is rainfall with a very low pH. The human eye has a pH value of 7.35, is just slightly basic. This is, coincidentally, in range with proper pH levels for a backyard waterfall. To have pH in balance adjust the water with additions of pH increasers (bases) or pH de-creasers (acids) to achieve the range of 7.2 - 7.8.
If testing of the water shows a pH value below 7.0 the water is in a corrosive (acidic) condition and you will need to add a base to bring the pH into a more basic range to prevent corrosion. It doesn't take too long for a low pH condition to weaken key components and pit the rocks and pool. Conversely, if the pH is above 7.8, we are in a scaling (basic) condition and must add an acid to bring down the pH to prevent the formation of scale or calcium deposits.
A close cousin of pH, the level of alkalinity in the water is a measurement of all carbonates,bicarbonates, hydroxides, and other alkaline substances found in the pool water. pH is alkaline dependent; that is, alkalinity is defined as the ability of the water to resist changes in pH. Also known as the buffering capacity of the water, alkalinity keeps the pH from "bouncing" all over the place. Low alkalinity is raised by the addition of a base (similar to pH); sodium bicarbonate is commonly used. High levels of alkalinity are lowered by the addition of an acid (similar to pH).
A very important component of water balance, alkalinity should be maintained in the 80-120ppm range.
When we speak of scale, we are talking about calcium carbonate which has come out of solution and deposited itself on surfaces. It is a combination of carbonate ions, a part of total alkalinity and calcium, and a part of the Calcium Hardness level. The test for Calcium Hardness is a measure of how "hard" or "soft" the water is. "Hard" water can have high levels of calcium and magnesium. If these levels are too high, the water becomes saturated and will throw off excess particles out of solution which then seeks to deposit themselves on almost any surface inside the waterfall. Calcium Carbonate scale is a white, crystallized rough nodule.
If the Calcium Hardness levels are too low, the water is under-saturated. If under-saturated, the water will become aggressive as it attempts to obtain the calcium it needs. Such "soft-water" will actually corrode surfaces inside the backyard waterfall which contain calcium (like pool and rocks) and other minerals to maintain its hardness demand.
Recommended range for calcium hardness is 200-400ppm. Calcium Hardness levels should be tested weekly with fresh reagents or strips.
Maintaining balanced water is the key to long term enjoyment of your backyard waterfall and swimming pool waterfall. Many pool supply stores will have testing equipment to test your water and provide you with the analysis of your water, as well as the supplies you’ll need to maintain a balance. Test kits are also available for you to check the water on a weekly basis.