Installing Your Pool, Stage 10: Your First Week Of Water Care

Where you are: pool built, filled, filtration running. If you are not there yet, go back to stage nine.

What you will have finished with: balanced, sanitised, clear water and a pool you can actually swim in.

Here is the part nobody warns you about. You have just spent a weekend building a pool, it is full of water, the pump is humming, and you still cannot swim in it.

Fresh fill water is untreated. It has no sanitiser in it, its balance is whatever your water source happens to be, and in warm weather it will start going bad within days if you leave it alone. The building is done. The pool is not finished.

The good news is that this is a few days of small tasks, not a big job, and once you are through it you have a routine that carries the rest of the season.

Do not add anything yet

The instinct is to dump in chlorine and start swimming. Resist it.

Test the water first. Fill water varies enormously depending on where it came from, and you cannot correct something you have not measured. Municipal water in one town is nothing like municipal water two counties over, and well water is different again.

Get a proper test kit, ideally a drop count kit rather than strips, and take a reading before you open a single container. Our water testing guide covers how to read the results.

You are looking at five numbers:

If you filled from a well, read this first

This one catches people out and it can permanently mark a brand new liner.

Well water frequently contains dissolved iron or manganese. While they stay dissolved, the water looks clear and fine. The moment you add chlorine, they oxidise, and you get brown, rust coloured or greenish staining that settles onto your liner.

If you are on a well, add a stain and scale preventer, also called a sequestrant, before you add any chlorine. It holds those metals in solution so they cannot drop out and stain.

It is a cheap product and it is much easier than dealing with a stained liner in week one. If you are unsure whether your water has metals in it, treat it as though it does. There is no downside.

The order to do things in

Order matters here, because these numbers affect each other.

1. Total alkalinity first. Alkalinity buffers pH. If you set pH before alkalinity, your pH will move again as soon as you correct the alkalinity and you will be chasing your tail.

2. Then pH. With alkalinity in range, pH becomes much easier to hold.

3. Then calcium hardness. Water that is too soft is aggressive and pulls minerals from whatever it can reach. Too hard and you get scale on your equipment.

4. Then stabiliser. Cyanuric acid protects chlorine from being burned off by sunlight. Without it, you will be adding chlorine constantly and wondering where it goes.

5. Sanitiser last. Once everything else is in range, chlorine works properly and stays around.

One thing at a time. Add a product, run the pump to circulate it thoroughly, then retest before adding anything else. Adding three things at once and testing afterwards tells you nothing about what did what.

Follow the label for your pool volume. Dosing is by gallons, and you worked out your gallons back in stage one.

Two chemical handling rules

Worth stating plainly because both matter.

Never mix chemicals together, and never add water to a chemical. Always add the chemical to water.

Store chemicals somewhere dry, ventilated, and away from the pool and equipment. Chlorine products give off corrosive fumes. A bucket of tablets sitting next to your steel wall or on your equipment pad will visibly attack the metal over a season. Our rust guide explains why that matters more than people think.

Run the pump

For the first several days, run the filtration continuously.

New water needs full turnover to distribute chemicals evenly and clear the fine dust that comes with new filter sand and construction. Intermittent running in week one just slows everything down.

Backwash if pressure rises. New pools often collect fine sediment quickly at first.

Once your water is clear and balanced, you can move to a normal daily run schedule.

Brush and skim

Not glamorous, but it helps.

Brush the walls and floor in the first few days. It lifts anything settled during construction and helps chemicals reach every surface.

Skim the surface daily. There will be more debris than you expect from a build.

Keep the skimmer basket clear. A blocked basket restricts flow, which slows everything you are trying to achieve.

When is it safe to swim?

Three conditions, and all three need to be met.

Chlorine in range. Free chlorine at 1 to 3 ppm, and if you shocked the pool, wait for it to come back down to that range before anyone gets in.

Balanced water. pH in range especially, because badly balanced water is uncomfortable and irritating.

Clear water. This one comes straight from your assembly instructions, and it is a safety requirement rather than an aesthetic preference:

It is important that all users be able to see the bottom of the pool. Foggy water must be cleared up before entering the pool.

If you cannot clearly see the floor of the pool, nobody swims. Not because it is unpleasant, but because you cannot see a person on the bottom.

Realistically, expect two to four days from filling to swimming. Sometimes faster, sometimes longer if your fill water needed work.

A realistic first week

Day one. Test everything. Add sequestrant if you are on a well. Start correcting alkalinity. Run the pump continuously.

Day two. Retest. Correct pH. Brush the walls and floor.

Day three. Retest. Adjust hardness if needed, add stabiliser, then begin sanitising.

Day four. Retest. Chlorine should be holding. Water should be clearing. Backwash if the filter pressure has climbed.

Day five onward. Confirm everything is in range, water is clear, you can see the bottom, and chlorine is between 1 and 3 ppm. Then swim.

And then it becomes routine. Test a couple of times a week, keep the numbers in range, skim and brush, and empty the baskets. Our pool maintenance guide covers the ongoing rhythm.

Before you call it done

• Water tested before anything was added
• Sequestrant added first if filling from a well
• Alkalinity corrected, then pH, then hardness
• Stabiliser added
• Sanitiser added last, with chlorine holding at 1 to 3 ppm
• One product at a time, circulated and retested between
• Pump run continuously through the first several days
• Walls and floor brushed, surface skimmed, baskets emptied
• Filter backwashed if pressure rose
• Water clear enough to see the bottom of the pool
• Chemicals stored dry, ventilated, away from the pool and equipment
• Safety labels fitted, barrier in place, ladder secured

The short version

• Fresh fill water is untreated. You cannot swim the day you finish filling.
• Test before you add anything. Fill water varies enormously.
• On well water, add a sequestrant before any chlorine or you risk staining a brand new liner.
• Order: alkalinity, pH, hardness, stabiliser, then sanitiser.
• One product at a time. Circulate and retest between each.
• Run the filtration continuously for the first several days.
• Brush, skim and keep the baskets clear.
• Swim only when chlorine is 1 to 3 ppm, water is balanced, and you can clearly see the bottom.
• Expect two to four days from full pool to first swim.
• Store chemicals away from your steel wall and your equipment.

That is the whole build

Ten stages, from a marked circle in the grass to a pool you can swim in.

If you have followed the series through, you have levelled a base, stood a steel wall, hung a liner, plumbed a filtration system and treated your first fill. That is a genuine piece of work, and the parts of it that felt hardest at the time are the parts that decide whether this pool lasts ten years or twenty.

The things worth remembering from here:

Keep the base of the wall dry and clear. Drainage and debris decide the lifespan of a steel pool more than anything else.

Keep your chemistry in range. It protects the liner and the equipment, not just the swimming.

Look at the pool twice a year. Ten minutes at opening and ten at closing catches almost everything.