Water testing

See also: Chemical Guide

SALINITY METERS SALINITY METERS measure the salt in the Total Dissolved Solids in ppt or ppm and give a very accurate reading of the salt content. Very useful for owners of salt-water spas, and pools with salt-water chlorination systems. These instruments will provide readings on a scale from at least 2000 to 7000 ppm and are far more accurate than test strips or cheap digital TDS meters.
For 4,000 ppm you need 40 kg of pool salt per 10,000 litres (10 m3, 2,642 US gallons) Salt is a part of Total Dissolved Solids, only a genuine salt meter will accurately display the salt level. Cheaper TDS meters display the total of salt and all other dissolved solids. For starting up, a typical average sized domestic pool, say 4 x 10m with an average depth of 1 metre (from about 0.7m to 1.40m deep) will need 160 kg or 7 x 25 kg bags of special TRS pool salt, but do not forget to include the volume of your balance tank (if any). Only special pool salt will provide a reasonably accurate ppm reading.

pH METERS: pH is a measure of the activity of the (solvated) hydrogen ion. Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline. The pH, which as every pool owner knows - or should know - must be kept within 7.2 - 7.6. What everyone does NOT know is that it is even more important to maintain the pH than the chlorine level - if the pH is not right, the chlorine won't work properly.

ORP TESTERS measure the ORP, also known as redox potential, oxidation / reduction potential, and measure the Chlorine in a fundamentally different, and far more accurate way than traditional PPM Test Kits with reagent drops, tablets, powders, or test strips. Operators of large or commercial pools must realize that basic test kit measurements are insufficiently accurate and can differ fundamentally from ORP readings.

COPPER TESTERS are essential for pools that are permanently disinfected by ionisers (Naked, etc.) or chlorine substitutes such as PurePool or NanoKleer, and when copper based algicides are used regularly. Test kits are available by Hanna electronic-photometric checkers, and Microtest (marketed by Naked) titration kits. The required concentration for using a copper based disinfection system is 0.2 – 0.5 ppm. Occasional shocking with small ammounys of chlorine may be required.

ALKALINITY TESTERS are used for testing the alkalininty beyond the parameters of the normal pH range when normal dosing with pH Minus or pH Plus does not result in a stable pH. Ideal Total Alkalinity Levels: Concrete Pools: 80 - 150ppm. Total Alkalinity should not be confused with pH, although the two are closely related. Total Alkalinity determines the speed and ease of pH change, it is measured in ppm. Low Total Alkalinity can cause unstable pH levels. This causes an inability to keep the pH constant and may cause staining, etching and corrosion of metals. High Total Alkalinity will cause constantly high pH levels.

HARDNESS TESTERS are are used to determine the level of calcium in the water. For pools (or homes) using well water in areas where the aquifer is in sedimentary rock (limestone), a hardness test is essential to prevent damage to swimming pool equipment, especially pumps, heaters, and salt water chlorinators. Ideal Calcium Hardness Levels: Concrete Pools: 200 - 250ppm Fibreglass/Vinyl Pools: 150 - 190ppm
In addition to pH and Total Alkalinity, Calcium Hardness must be kept in balance so that your pool water does not become too corrosive or end up scaling the surface of your pool.