Pools, hot tubs, and the machine underneath them
A pool is a machine, a set of numbers, and a year.
We are pool owners and researchers, not licensed technicians or electricians. This site explains how the machine works, what its numbers mean, and what the pool needs at each point in its year — so you can tell a nuisance from a job for a professional.
Everything on this page describes that pool: the sequence it runs in, the water you can see, the year it moves through, and the numbers that keep it clear.
The sequence
The clarity scale
What you can see, and what it usually means
The one reading you can take without a kit. The green panel stays on this page on purpose — it is the state most owners actually meet, usually in the first week after the cover comes off.
An almanac for the pool year
What does the pool need now?
A pool’s year has six states. Pick the one you’re in — or go to the middle, for the things that are true all year.
Showing Opening — typical for the first warm weeks north of the equator.Showing Running — typical for the long settled middle of a swimming season.Showing Under load — typical for late summer north of the equator.Showing Closing — typical for the first cold nights in a freezing climate.Showing Dormant — typical for a covered pool in a freezing climate.Showing Any time — the things that stay true whatever the pool is doing.Not your pool? Pick any state. Many warm-climate pools never close, and a hot tub’s busiest season is winter.
Opening
The cover comes off, the plumbing refills, and water moves through the filter for the first time in months — usually while the chemistry is still nowhere near where it needs to be.
The jobs
- What Actually Happens When a Pool Is Opened for the Season?
- When Does a Pool Filter Need Cleaning, Not Backwashing?
- What Does Backwashing a Filter Do? A Clear Answer
- What Is Phosphate in Pool Water, and Does It Matter?
What goes wrong now
Running
The long settled middle of the season. Nothing dramatic happens, and the work is small corrections made often rather than big ones made late.
The jobs
- Winter Cover vs Solar Cover: What Each One Actually Does
- Bromine vs Chlorine in a Hot Tub: The Real Difference
- How Long Do Pool Pumps and Filters Typically Last?
- What Does a Filter Pressure Gauge Actually Tell You?
What goes wrong now
Under load
Warm water, long sun and heavy use burn through sanitiser faster than at any other point in the pool’s year, while the filter takes on more debris than it was sized for.
The jobs
- What Is Biofilm in a Hot Tub, and Why Does It Matter?
- How Is Hot Tub Water Chemistry Different From a Pool?
- What Is Scale and Why Does It Form in a Pool?
- Dealing With Pool Leaves Without Wrecking the Equipment
What goes wrong now
Closing
Everything that can freeze has to come out, and everything that stays has to be able to sit for months without attention.
The jobs
- Safety Cover vs Winter Cover: What’s the Real Difference?
- Winter Cover vs Solar Cover: What Each One Actually Does
- Should a Pool Be Drained for Winter? The Real Answer
- What Does Winterising a Pool Involve? A Clear Guide
What goes wrong now
Dormant
Covered and still. Very little to do, and a short list of things worth checking so that opening is not a rescue.
The jobs
- Safety Cover vs Winter Cover: What’s the Real Difference?
- Winter Cover vs Solar Cover: What Each One Actually Does
- How Long Does a Hot Tub Cover Last, and Why It Matters
- How Often Should Pool Water Really Be Replaced?
What goes wrong now
Any time
The things that stay true whatever the pool is doing — how the machine works, what the numbers mean, and where the site stops.
The jobs
- What Does Pool Maintenance Actually Take Each Week?
- What Questions Are Worth Asking a Pool Builder?
- The Ongoing Pool Jobs Nobody Mentions Before You Buy
- Above Ground vs In Ground Pool: The Real Difference
What goes wrong now
What the numbers mean
One example pool, drawn as positions rather than targets. Yours will differ — always follow your own test kit.
A number outside its band is information, not an emergency — it tells you which job is next. We do not publish doses, and the order on the strip above matters more than any single reading.
Recently
Newest on the site
Everything, by subject
Where things live
Where this site stops
We explain how things work and what readings mean. We do not publish doses, we never describe mixing chemicals, and anything involving gas, bonding, electricity or structure belongs to a licensed trade. No device on any page removes the need for supervision.
- Anything electrical near water — a licensed electrician, every time.
- Gas heaters and their flues — a qualified gas engineer.
- Bonding and grounding — not a DIY job, and not a visual check.
- A cracked shell, a moving coping stone, a pool that will not hold water.