If one corner of a pool always has leaves in it and one section of the wall always grows algae first, the cause is almost never the chemicals. It is circulation, and circulation was decided when the shell was laid out.
Skimmers work with the wind
Surface debris moves where the wind pushes it. A skimmer on the upwind side is fighting the wind all day; one on the downwind side gets fed. In the Triad the prevailing summer wind is generally out of the southwest, which is a reasonable default when there is nothing else to go on.
Better than a default is looking at the actual site — houses, fences and tree lines redirect wind at the scale of a backyard, and the pattern on your lot may have nothing to do with the regional average.
Returns should push water toward the skimmer
The job of the returns is to move surface water across the pool to where the skimmer can take it. Angled correctly, they set up a slow rotation across the whole surface. Angled badly, they set up a circulation loop in half the pool and leave the rest still.
Return eyeballs are adjustable, which means some of this can be tuned after the fact. What cannot be tuned after the fact is how many returns there are and where they penetrate the shell.
Where dead spots come from
- Steps and benches, which sit outside the main flow almost by definition.
- Tight inside corners on freeform shapes.
- The far end of a long rectangle with returns only at one end.
- Under a tanning ledge, if the ledge has no dedicated return.
- Behind water features that break up the surface flow.
Each of those is solvable in design — an extra return, a dedicated ledge jet, a shape adjustment. None of them is easy to solve once the gunite is shot.
Ask for the plan
Any builder should be able to show you where skimmers and returns are going and explain why. If the answer is that it is standard, ask which way the wind comes across the yard. The response tells you a lot.
What it costs you if it is wrong
More brushing, more chemical, more filter runtime and a section of wall that always looks worse than the rest. None of it is catastrophic and all of it is permanent, which is exactly why it deserves attention while the plan is still on paper.
How many skimmers
One skimmer handles a small pool. Larger pools, and any pool with significant tree exposure, benefit from two — and two skimmers positioned to work with the wind from different directions handle the reality of a backyard where the breeze is not consistent.
Two skimmers also give redundancy. A single skimmer blocked by a heavy leaf load stops surface circulation entirely until somebody clears it. With two, the pool keeps working.
Main drains are about circulation, not draining
The name misleads people. A main drain rarely drains anything; its job is to pull water from the bottom of the pool so the whole volume circulates rather than just the top layer. Without it, water near the floor turns over slowly and chemistry stratifies.
Modern installations use dual drains with anti-entrapment covers, which is both a safety requirement and better hydraulics. Any pool being remodelled should have this brought up to current standard while it is empty.
Tanning ledges need their own circulation
A shallow ledge is warmer, shallower and more used than the rest of the pool, which means higher chemical demand and more debris. A ledge served only by the main pool circulation develops problems first, almost every time.
A dedicated return or a bubbler that doubles as circulation solves it, and it costs very little at construction. This is one of the most common things we correct on renovations of pools built by others.
Testing it after startup
Once the pool is running, a simple test tells you a lot: drop a small amount of dye or a floating object at several points and watch where it goes. Anywhere it sits still is a spot that will collect debris and grow algae first.
Return eyeballs can then be adjusted to improve it. It is worth doing this deliberately in the first weeks rather than discovering the dead spots over a season.