For Window Cleaners, this is the golden question.
Unfortunately, there isn't a straight answer. There are too many variables, some of these are in your control, and some are not. Below, you'll find some handy tips and metrics to help you estimate it thought!
For the uninitiated, deionizing resin is a consumable component, found in Window Cleaning systems to purify water. It can be used as part of a 4 stage RO/DI filtration system, or as a stand alone means to purify water (for more on these, check out our article types of filtration, RO/DI or DI Only).
How long your resin will last before it stops purifying the water sufficiently will be dependent on a number of variables, but there are a few major things that effect its life, more so than others.
These are:
Size of the DI vessel (volume of resin)
Quite simply, the bigger the vessel, the less you require the resin to be changed. Two of our most common sizes are 11L & 25L, however there are plenty of other sizes available. As you might expect, the 11 Litre will need replacing more often, but a 25L bag of resin will provide two full refills of this size vessel. There are also long life vessels such as the HydroPower, that distribute the water more evenly through the resin, improving the amount of pure water you can create from the same volume of resin.
Total dissolved solids of the input water
Tap water is classified as hard or soft, however in reality it's not quite so black and white. In the UK, Tap water TDS readings range from 30ppm to 500ppm (parts per million), and knowing where you fall on this scale will give you an idea of the lifespan you can expect from your resin.
Getting a reading from your tap can be done with a TDS Meter - and can help you determine which type of filtration you should be using. For the sake of simplicity, we usually advise that water under 150ppm is considered soft, anything above is hard water. In a soft water area you can be looking at a few months between resin changes, by comparison, hard water can go through resin in a few days (and this is where a more complex filtration systems can lower running costs).
Water usage per day
The final thing influencing the life of your resin is the number of litres of water you are purifying. A system using 650 Litres per day is going to need changing far more often than a single operator using only 300 litres.
The best way to get a fixed idea on the life of your resin is through trial and error using the equipment. Begin by tracking how many litres of pure water you use every day, and the size of the filtration system you are using. When your resin stops reading 0ppm (measured on a TDS meter) it's time to change and now you have an estimate of how long you will get from a single refill.
Even this won't give an exact timespan, as tap water TDS readings are known to change from time to time, you will often find changes even between seasons, but it does give you a ballpark you can work with for managing your resin. In order to budget, it's important to regularly check the lifespan of your resin and keep a record.
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