The installation of new evaporative pads is expensive. The material should last at least two years if not more. With good regular maintenance, evaporative pads should last 5 years. Fortunately the grower has the opportunity to spend very little money on small items which will increase the lifespan of the evaporative pad. Considering the cost of a new pad and the cost of regular maintenance over a period of time, it is worth while spending a little more time in ensuring a clean evaporative pad. Following are the minimum maintenance activities the grower should carry out to ensure maximum life and efficiency of the evaporative pad.
The water in the sump supplying the evaporative pads should be treated with a wetting agent. Wetting agents decrease the surface tension of the water allowing for a thinner layer of water on the surface of the pad, increasing air flow rate and surface area of water exposed to the air. The cheapest wetting agent is dish washing soap. Compliment®, which is used in combination with fungicides, can also be used but is slightly more expensive.
It is good practice to add some type of algaecide. This will keep the evaporative pads open for efficient air flow. The air flow of the pad will decrease as it gets older, this is inevitable, but good maintenance will ensure higher flow rates. A cheap algaecides are those that are used in swimming pools. Many growers add stabilized chlorine tablets that should last for at least a month in the sump. These work the best. Ensure that the pH of the water is between 5.8 and 6.5.
A good practice is to add non volatile insecticides in the sump. This will reduce the amount of insects entering the greenhouse and reduce the amount of insects breeding in the evaporative pads material.
Add a filter between the pump and outlet will prevent the evaporative pad clogging up with muck and other debris. The clogging of the evaporative material is one of the quickest ways of reduce the efficiency of the pad. Not only does muck and other particles reduce the lifespan and efficiency of the pads, they also attract insects and algae which further reduce the lifespan of the pads.
It is good practice to hose the pads down for salt and algae build-up. This should be done once a month depending on salt content of water and algae build-up on the pads. The water should also be flushed and replaced with clean water each month. Salts tend to build-up in the sump because the salts do not evaporate as the water does. So over time the salt concentration will increase and cause damage to the pads.