Public pools must comply with water quality and air quality requirements, but it is often difficult to know how well a pool is actually performing or to compare one pool against another. The Dryden Aqua Performance Factor (DAP Factor) is an easy approach used to quantify the performance of any pool water treatment system. The DAP Factor can be used as a tool to mitigate the risk to the public, pool staff and avoid structural damage to the building, as well as a tool to help reduce running costs and save money. Indeed we have found that a typical public pool could save between 30% and 50% of their running costs, but only if you are aware that there is the possibility to improve performance. In this context the DAP Factor lets you know how well you are performing, or if there is scope for improvement.

Most pools with high rate sand filters have a DAP Factor over 6, we can normally reduce the DAP Factor to less than 2 by modifying the existing system, which makes for a 70% to 80% saving in chemicals and water, plus a 15% energy saving, which all translates into a 30% to 50% reduction in running costs. The cost of the system improvement can usually be recovered out of revenue savings in less than 12 months.

The DAP Factor is based on a simple approach; the less chlorine used per bather, the better the system performance. The DAP Factor is therefore a unifying measurement which encompasses all chlorinated public and private swimming pools irrespective of the size or design of the facility, because it is calculated from two simple measurements;

A zero chlorine demand would be impossible, but a DAP Factor under 1 can be achieved, and is considered to be the best possible water quality that cannot be surpassed. A DAP Factor under 1 also means you have eliminated most of the chlorine by-products and have near perfect air conditions above the water and in the pool building. Dryden Aqua has now achieved this objective in public pools, which means we have reached the end-point of pool water treatment. Dryden Aqua Integrated Water Treatment Systems simply can not be beaten, Pool Water Treatment problems are now solved and we manufacture the products that allow you to achieve the best possible results and lowest running costs.

DAP factor Kg.Cl₂/day/1000 bathers	Comment	DAP Factor implications
< 1	Well operated and managed pools.	Extremely low risk associated with water quality and air quality, achieved using Dryden Aqua fully Integrated system operated properly with good overall hygiene and pool management. AFM, ZPM, APF, ACO and ZPMr. DIN standard Filters operating at less than 15 m/hr
1 - 1.9		Very low risk associated with water quality and air quality, very good pool, fitted with AFM, ZPM and APF. Filters operating at less than 20 m/hr
2 to 3.9		Low risk pool but could do better. There may be high combined chlorine but no smell or sore eyes which indicates organic chloramine but low inorganic chloramines. Pool may be using AFM but flow rates are too high or poor quality filters are used. There may be equipment or operational problems. Filters operating at less than 25m/hr
4 to 4.9	Typical of public pools that could do better and save up to 50% of water treatment running costs. Return in capital investment out of revenue saving approx 12 to 18 months after installing AFM, ZPM,APF and ACO	Low to medium risk pool, staff may be at risk from respiratory issues, there will be a distinct smell of nitrogen trichloride, some of the public may complain about sore eyes. There may be a risk to regular bathers. Performance Factor is typical of sand filtration systems operating at water flows below 25 m/hr with poor coagulation and flocculation.
5 to 5.9		Medium risk, staff may be at risk from respiratory issues. Some of the public will complain of sore eyes and skin irritation or allergic reactions. Regular users of the pool may be at risk from respiratory issues. Performance Factor is typical of sand filtration systems operating at water flows above 25 m/hr with poor coagulation and flocculation.
6 to 7.9		Medium to High risk pool, staff and public are at risk, structural damage to the building and stainless steel may be evident. High levels of trichloramine, probably also high levels of volatile lipid soluble organic and inorganic chlorine molecules such as chloroform and cyanogen chloride. Potential health risk to children under 2 years of age.
8 to 10	Poor quality pools that should instigate immediate improvement to procedures and equipment. Return in capital investment out of revenue savings usually well under 12 months after installing AFM, ZPM,APF and ACO	High risk associated with using the pool or for the staff working in the pool environment. Potential bio-hazard from bacteria, oocysts, bacteria exotoxins and endotoxins. Public may experience an allergic response to the pool water and / or the atmosphere. Increasing potential risk of health problems especially for children under 2 years of age because their blood:brain barrier is not fully developed.
>10		Very high chlorine consumption indicative of a poor system design and operating conditions. In the opinion of Dryden Aqua any pools with a DAP Factor greater than 10 should be treated with extreme caution, especially for the pool staff, children, elderly or immune depressed individuals. The water and air quality may be okay but only if the pool is exchanging or dumping large quantities of water. High chlorine demand may also be experienced with UV and ozone systems.

The Dryden Aqua DAP Factor for a swimming pool relates the chlorine oxidation demand for 1000 bathers per day expressed as Kg of chlorine used. The first step is to work out the available chlorine in the product that you use in your swimming pool; this will be a variable so check the product data sheets for an accurate figure. The most common forms and values are as follows;

1.Calcium hypochlorite, chlorine is approx equal to 0.68 x the Kg of calcium hypochlorite used per day
2.Sodium hypochlorite solution, chlorine is approx equal to 0.12 x the litres of sodium hypochlorite used per day

Example; in a well operated pool using AFM, APF, ZPM and the clients filters

Average bather load per day = 1150 per day
Average calcium hypochlorite consumption per day 1.8 kg
Chlorine level in 1.8 kg of calcium hypochlorite = 1.8 x 0.68 = 1.22 kg per day for 1150 bathers
Relate the chlorine consumption to 1000 bathers = 1000/1150 x 1.22 = 1.1 = DAP Factor = a very good pool

Back-wash frequency 1 - 2 times per week increasing to 1 time very second week (water quality and bather load dependent), back-wash duration normally less than 5 minutes