Every pool in Arizona eventually needs its water fully drained and its surface acid washed. This is not a sign anything went wrong. It is normal maintenance on a normal schedule, and most pools here need it every 3 to 5 years because of exactly the conditions that make Arizona pool ownership what it is: heat, evaporation, and hard water, year after year.
Why it happens on a schedule here
Water is never actually static in a pool. It evaporates, gets topped off, evaporates again, and every cycle concentrates dissolved solids a little more, the same process that drives calcium buildup on tile and equipment. Given enough years, no amount of chemical balancing can undo what has accumulated in the water itself. At some point the water needs to be replaced outright, not adjusted. That is the drain part. The acid wash addresses what has built up on the plaster surface itself over the same stretch of time, stains and scale that brushing alone cannot remove.
The signs to watch for
You do not need to guess when this is coming. A handful of clear signals show up before a pool actually needs a drain and acid wash.
Total dissolved solids reading high. TDS is a measure of everything dissolved in the water, salts, minerals, metals, and byproducts that build up over years. Once TDS climbs high enough, chemicals stop working efficiently no matter how carefully they are dosed, because the water itself is saturated with everything else. This is usually the clearest technical signal that a drain is coming, and it is something worth testing for specifically rather than assuming from other symptoms alone.
Chlorine will not hold a level. If you are adding chlorine and it is disappearing faster than heat and sunlight can explain, and the water is not green, that can point to high TDS or high cyanuric acid interfering with how the chlorine functions. Old water gets chemically stubborn.
Stains that will not brush out. Metal stains, organic stains, anything that has bonded to the plaster and stays put no matter how much you brush. Fresh staining often responds to brushing or targeted treatment. Stains that have set into the surface over time usually need the surface itself addressed, which is what an acid wash does.
A calcium line that will not come off. Related to hard water buildup, but at some point a waterline scale deposit gets thick and set enough that brushing and normal scale removal do not touch it anymore. That is a surface problem, not a water chemistry problem, and it needs the surface treated directly.
None of these individually always means drain and acid wash. But when two or three show up together, especially TDS plus stains or scale that will not respond to normal treatment, that is a strong signal the pool has reached the end of its water life.
What the job actually involves
A drain and acid wash is exactly what it sounds like in sequence. The pool gets fully drained. Once empty, the plaster surface gets washed with a diluted acid solution that dissolves the top layer of buildup, stains, and scale, revealing cleaner plaster underneath. The surface gets rinsed, the pool gets refilled, and the water chemistry gets rebuilt from scratch, which takes its own process of balancing pH, alkalinity, and sanitizer levels in new water.
Why summer draining needs extra care
Draining a pool in Arizona summer is not the same job as draining one in October, and it is not something to take lightly during the hottest months.
Plaster damage in heat. An empty pool shell sitting exposed to 110 degree direct sun can actually take heat damage to the plaster surface itself. Plaster that dries out and heats unevenly can crack or develop surface damage that was not there before the pool was drained. Timing and surface protection during an empty period matter more in July than in cooler months.
Hydrostatic pressure. Underneath every inground pool shell, groundwater exerts upward pressure against the pool floor. Normally the weight of the pool water pushes back and keeps everything stable. Drain the pool and that balance is gone, and if groundwater pressure is high enough, it can actually push up on and crack an empty shell. This risk exists any time a pool is drained, but summer monsoon rains raising the local water table make it a real consideration for timing a summer drain specifically. Pools with a known high water table sometimes need hydrostatic relief plugs opened during the drain to equalize pressure safely.
Neither of these means summer draining cannot be done. It means it needs to be done with the right precautions, not treated the same as an off season drain.
The bottom line
If your pool is 3 to 5 years out from its last drain and you are seeing high TDS, chlorine that will not hold, stubborn stains, or a calcium line that will not budge, it is worth getting the water tested properly before assuming the fix is more chemicals. Sometimes the water itself is just done.
We handle drain and acid wash jobs for homes across the West Valley, with the summer precautions built into how the job is planned and every visit documented in an emailed report. Read more at /residential/drain-and-acid-wash.
