Guaranteed to bring out someone to defend Desjoyaux, that's why they are so successful. Despite all the evidence they still get a following, that's what intrigued me so much and prompted me to do far better.
Now I didn't say it doesn't work but there are far more efficient ways of doing things.
My experience as a pool professional is I have years of hands on on lots of pools whereas many owners are on their first or possibly second but as you bought Dessy again you don't know how much better things can be.
"The filtration works perfectly" Does it? Well it's not so much filtration as a strainer bag that cannot physically capture anything small, Bacteria and virus's are small and those which are not killed by chlorine have to filtered out so thankfully they are at the moment rare but they do exist like cryptosporidium. You cannot use flocculent to capture small particles with Dessy bags so an algae problem goes on and on for ages with cloudy water that can take more than a week to eradicate.
That's one big difference when something goes wrong (especially if you are renting) how quickly can we get the pool back into shape.
That means the electricity you are using is straining out the larger stuff but the rest is just going around and around only it doesn't do that very well either. Not too bad on a small pool but as they get larger 8m x 4m + the situation gets worse. This is for two reasons.
1. The skimmer and single return jets are very close together, the water leaves the return jet and moves about half way up the pool before it runs out of steam, some of the water doesn't go that far and does a quick U turn and back into the skimmer.
2. The filter bags are on the pump intake and trying to suck water is very inefficient, water behaves like air and is better pushed. Try it for yourself, try sucking out the candles on a birthday cake compared to blowing them out. Same lungs different result.
Running costs less than €100 pa, well that depends on how short a period you run for but as the standard Dessy setup includes a less than efficient salt chlorinator (more efficient ones are available) . They also use dedicated pumps so when one fails the shock of an €800+ replacement has never sat well with any customer I have met as it's around 3 times the price of any other pump.
Negates the need for a separate pump room, They use a monoblock setup for quick and easy install as they can't trust the unskilled monkeys to be able to join pipes and drop in is much more profitable. Whats wrong with an area put aside for the equipment? I could just as easily state the large ugly plastic covers are hideous compared to tucking away the equipment out of sight.
Antiquated sand filters? Your drinking water is delivered via antiquated sand filters why? because they work far better the a strainer bag. Pathogenic micro organisms that pass straight through the dessy bags get trapped in sand filters and with flocculation available even the tiniest parts of oocysts can be caught and filtered out. That is important because the more you remove by filtration the less chlorine is required to maintain the pool and that means less of the volatile disinfection by products we don't want that can trigger asthma etc. That means every euro of electricity is actually removing more and more of what you don't want from the water rather than recirculating it.
Desjoyaux was designed by a Frenchman, so what? Ask the professionals and make your own judgment, well I am a professional but I am grateful to Desjoyaux, over the years going out to work on those pools has made me an income. It is also the main reason why I designed the low energy pool as I realised if something as bad as Desjoyaux can actually work with such poor water flow if I used slightly better flow and circulation how much lower could I get the energy usage? Answer very low. My pool filtration uses about the same as an old standard light bulb to run per hour (50 watts) I have also engineered other pools as large as 12m x 6m and that stays beautifully clear on 86 watts which is a long way down form the 2.2kw pump that was "designed" for that pool.