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Wow, thanks for the answer. Another question-
I’m pretty lax when it comes to car washing, and my car is getting pretty dirty now. With water restrictions here in Sydney, it’s given me an excuse to continue to avoid washing my car. How much water is used during an express exterior carwash?
Oh, and how much should I expect to pay for a really good exterior clean?
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It really depends on the water usage issue. Some carwashes use a lot more fresh water than others depending on a variety of factors, water tap fees, the cost of fresh water, whether they have a water reclaim system, etc.
Just our final Reverse Osmosis rinse alone is about 9/gal per car. We however use a water reclamation system that operates very much like a biological filter in an aquarium.
Every carwash has a trench (or pit, as it’s lovingly referred to as it’s so much fun to work on something in there) where the water rushes into beneath the vehicle. This water (at least at our wash) runs through a collection pipe and is flowed into our series of underground tanks that are built into the concrete lot.
The first tank is the collection tank, where much of the heavy sediment settles to the bottom and there’s a spillover “window” into the next tank, where the water is aerated (to reduce the smell) and pumped into a hydrocyclone system by these huge grinder pumps. The hydrocyclones then use centrifugal force to "spin off’ and seperate the heavier water from the lighter water. The heavier water with more solids in it is rejected back into the collection tank, the lighter water is sent to a bioreactor, where special living enzymes that are bred to feed specifically on carwash residues, remove most of the soaps, waxes (but not dyes, as in colored soaps) from the water.
These enzymes are pretty prolific in the way they reproduce, so then that water is pumped over into what’s called a plate seperator. The plate seperator is where the bugs (enzymes) go to die. There’s a huge plastic biomass set of plates in there that the bugs cling to, and then they die as they are deprived of their food supply. The dead bugs are pumped off the bottom out to the city sewer as they are biodegradable, and the finished product is what we call “clean” reclaimed water.
Reclaim water can only be used in certain applications, none of which includes rinsing, as the reclaim water has a very high TDS (total dissolved solids) count and will spot a car horribly.
I am not exactly sure how much water we use per car, but it’s somewhere in the 50 gallon per range, with about half that being reclaim water (which is again reclaimed, over and over, with the fresh water needed to add to the system to replace evaporation and drip off water).
We charge $8, $11 and $14 for our carwashes, but prices vary all over the place in proportion to volume. Many washes in the US north have very cheap washes as low as $3 or $4 dollars, but their chemical and labor costs are really low and they run at such a volume that they can afford to offer that price. I doubt they make any money at that point, the trick is selling upgraded washes where your profit margin is much higher and your increase in chemical costs is marginal.
You should pay whatever the market bears. You’re in AUS, so I have no idea what a decent carwash would charge. I would say no more than $10 US for a good wash and mechanical dry.