Module 01
How a pool works
One loop, six parts. Once you can picture the loop, most customer questions answer themselves.
A pool is a circle, not a container
People think of a pool as a big bowl of water sitting still. It is not. A working pool is water in constant motion, being pulled out, cleaned, treated, and pushed back in, all day, every day.
When a customer has a problem, the loop has almost always stopped doing its job somewhere. Your first instinct should be to ask where.
Tap or select any part of the loop to see what it does, how it fails, and what the customer says when it does.
Water is pulled out at the skimmer and main drain, cleaned and treated across the equipment pad, and pushed back in through the returns. One loop, always moving.
That is the whole thing. Everything else in this course hangs off that one sentence, so learn it well enough to say it out loud without thinking.
Where the water comes from
Water leaves the pool from two places at once, and the balance between them matters.
| Source | Takes | Roughly |
|---|---|---|
| Skimmer | Surface water, catching leaves and bugs before they sink and rot | 70 percent |
| Main drain | Bottom water, the coldest and stillest part of the pool | 30 percent |
Surface debris is easy to remove while it floats and much harder once it sinks. That is why the skimmer does most of the work.
The pump is the heart
Nothing else in the loop matters if the pump is not running. No filtration, no heating, no sanitizer reaching the water. A pool with a dead pump starts going backwards immediately.
The whole volume of the pool needs to pass through the filter regularly. A rep does not need to calculate that. What a rep needs is the plain version.
The filter, and a fact that sounds wrong
Three kinds of filter are common, and they trap different sized particles.
| Filter | Traps down to | Trade off |
|---|---|---|
| Sand | Roughly 20 to 40 microns | Cheapest to run, coarsest cleaning, backwashed to clean |
| Cartridge | Roughly 10 to 30 microns | No backwashing, so no water wasted, cartridge gets hosed and eventually replaced |
| DE | Roughly 3 to 5 microns | Finest cleaning available, most maintenance, powder recharged after backwashing |
Here is the part that sounds backwards. A slightly dirty filter cleans better than a spotless one. Debris caught in the media narrows the gaps, so it catches finer particles than it could when new.
Customers assume clean equals better and sometimes ask why we are not cleaning the filter constantly. Now you know the answer.
The single most useful thing in this module
Customers say "the water is barely moving" all the time. That one sentence has two completely different causes, and telling them apart is most of the diagnosis.
Pressure high, flow weak
The filter is dirty. Resistance has built up after the pump. This is normal, expected, and exactly what a scheduled filter clean is for.
Pressure low, flow weak
Something is starving the pump before water gets to it. A low water level, a blocked skimmer or pump basket, a valve turned part way closed, or air leaking in. This is not a dirty filter, and treating it as one wastes a visit.
Air in the system
Three complaints all point at the same cause:
- Bubbles coming out of the returns
- The pump basket filling with air instead of water
- The pump suddenly sounding louder
All three mean air is being pulled in on the suction side, before the pump. Usually a low water level letting the skimmer gulp air, a worn seal on the pump lid, or a loose fitting.
Noise
A pump that has started grinding or rattling usually has a blocked impeller or a failing bearing. Either way it needs a visit. There is no phone fix for a noisy pump, and a bearing that is left alone takes the motor with it.
What to hold on to
- Water goes out, gets cleaned and treated, comes back. One loop.
- Most water comes off the surface, through the skimmer.
- No pump running means nothing else is happening.
- A slightly dirty filter cleans better than a brand new one.
- High pressure with weak flow is a dirty filter. Low pressure with weak flow is something starving the pump.
- Bubbles, a loud pump, or an airy basket all mean air is getting in before the pump.
Knowledge check
Six questions. You need five to pass. Wrong answers explain themselves, so read them.
1. A customer says their pool water is barely moving, and the pressure gauge is reading higher than usual. What is most likely?
2. Roughly how much of a pool water should be coming from the skimmer rather than the main drain?
3. A customer asks why you do not clean their filter every single week to keep it spotless. What is true?
4. A customer reports bubbles coming out of the return jets. Where is the problem?
5. Which filter type traps the finest particles?
6. A customer says their pump has started making a loud grinding noise. What is the right move?