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Preventive Maintenance

Losing Water in your Pool – Is it good or bad?

By May 30th, 2019No Comments

Customers often ask, “How much water should we lose in our pools?” Sure, there is some confusion in the industry, but here are some snippets from of an upcoming industry magazine article that addresses water loss. Hopefully, that will help us clear up any confusion.

Is water loss good?

A moderate amount of water loss in a commercial pool is beneficial for several reasons including: positive control over excessive concentration of impurities and Total Dissolved Solids (TDS), and assistance in reducing bather skin and eye irritation complaints.

Optimum proactive water consumption should be at 4 gallons per bather, so if a site has 400 bathers a week, they should have added about 1,600-gallons of new water during that time in order to keep irritants at bay. The old adage of “the solution to pollution is dilution” is very true.

However, water loss of much more than 4-gallons per bather could be considered excessive and can lead to exponential consumption of chemicals, a rise in heating cost, and an adverse effect on water balance, leading to under-saturated or “hungry” water. 

New water consumes more chemicals

Why? Excessive water loss means that the pool will be filled with city water or well water. Both of these have Oxidation Reduction Potential (ORP) or 350-450 mV, much lower than the existing pool ORP level of 700-850. In fact, it takes quite a bit of chemicals to clean up a pool full of “new water”, which often looks greenish and dingy, to crystal clear and sparkling blue pool water. Chemical consumption for new water replenishment is often up to 10 times higher than maintaining the ORP level of existing water.    

New water dilutes your stabilizer:

Excessive water loss also quickly dilutes the stabilizer level in a pool. Stabilizer protects chlorine from rapid deterioration from sunlight and is an integral part of cost control in municipal pools. Maintaining a 10-30 PPM stabilizer level normally cuts chlorine consumption in half, but the water loss quickly dilutes the stabilizer, negating any potential savings and thus nearly doubling the overall cost of chlorination. New CDC guidelines suggest that 10-12 PPM of stabilizer is best when you consider the effects of fecal accidents, but a diluted stabilizer level will cost you lots of money just the same.

New water adds phosphates & promotes algae:

Another negative of excessive water loss appears when the incoming city water is high in phosphates. Phosphate compounds are used in municipal water supplies to protect piping from deterioration, but once deposited in the pools can cause severe issues. First, research shows that phosphates can mess up your chlorination a bit, but more importantly they provide a ready source of “food” for algae, making it almost impossible to keep a pool algae-free.

New water messes up your water balance.

City water is not optimum pool water. Why? First, most water supplies are low in calcium (80-120 PPM) and alkalinity (40-70 PPM), and thus contribute to aggressive water. By comparison, best practice dictates that pools should have calcium levels >300 PPM and alkalinity levels between 80-120 PPM in order to prevent deterioration of pool surfaces, heaters, pumps, and all metallic components.


Using less than 4 gallons per bather will often cause complaints, but losing too much water through leaks can cost you lots of time, money, and drama. It is important to keep track of your water consumption and make sure that you’re not using too much or too little, as there are negative consequences either way. There are a couple of new tools to help you win this battle, such as CES’s water consumption monitoring – which keeps track of water loss and can even alert you of an out-of-control situation. Also the new CES SpinDisc test kits help you keep more accurate control over your stabilizer levels.

So it pays to watch your water… and please let us know if we can assist you in any manner.

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