How to Test and Fix Pool Water


How to Test and Fix Pool Water

Learning how to test and fix your pool water and learn the skills involved to be your own pool guy or girl has never been easier and it’s a great skill to have especially with our current global situation.

Pilbara Contracting Pool Shop has recently launched our online store, we can now deliver any item you require to maintain your pool straight to your front door! You don’t even have to leave your house! Or poolside for that matter. That said, take a look at our super simple DIY pool water test and fix guide.

We will get you acquainted with what each chemical level means, troubleshoot the various reasons why levels could be too high or low and teach you the tricks of the trade-in determining how to avoid imbalanced chemical levels in the future, suggesting ways to bring your water balance back to its optimal levels.

But, before we ‘dive in’ if you get stuck or you have any questions regarding this article, the results of your water testing or you are unsure of what to do next; call us at the pool shop! We are always happy to help offering practical professional advice on what needs to be done to fix your pool water and how to maintain it.

The first thing you need to do is test your pool water this will determine where chemical levels are sitting. If you already have a test kit no worries you can still follow our suggestions, though we will be referring to our favourite basic test strips throughout this article. Quick Check Test Strips, discover if your chemical balance is too low, too high, or just right!

swimming pool water testing strip karratha

For home testing, test strips are our personal favourite. They’re easy to use and very accurate – much more accurate than using a liquid test kit because of human error when it comes to matching up the colours and using chemical droplets.

So, using your test strip, submerge it in your pool water (about an arm’s length down) for 10 seconds. Then, hold it still in the air for about 10 seconds (do not shake off the excess water). Then, match up the colours of the strip to the back of the bottle to get your readings. (We recommend testing your water from the same area in your pool every time).

Use your Test Strips to run through the below results from top to bottom of the test results strip:


Too low

What does too low mean?

Having low calcium hardness levels means the water is very aggressive and is extracting the calcium out of the pool walls (concrete pools only) which appears to be a crystallisation of calcium build up. The common mistake is that people assume this is due from TOO MUCH calcium, which is not the case. Aggressive water can also damage metal equipment (salt cells, heating elements etc) prematurely due to corrosion.

How to fix it?
You need to INCREASE your calcium by dosing your pool with Calcium Up. You can follow the dosing instructions on the back of the packet, though we recommend adding the whole 4kg bag to your pool for optimum results.

Too high

What does too high mean?
If the water is saturated with calcium, you will see scaling on pool equipment (salt cells, heating elements) causing reduced efficiency in these products. Pool water can also become cloudy.

How to fix it?
You need to reduce it by adding Calcium Down, though while doing this please note you’ll also have to regularly test and balance the pH to ensure correct levels are maintained (which we touch on further down in this guide).


Too low

What does too low mean?
Oh no! Your pool isn’t optimally sanitised. Possible middle ear infections and a green or cloudy pool is on the horizon!

Reasons it could below:

  • Not enough salt in the water for your Chlorinator to produce chlorine (salt should sit around 5000ppm (parts per million)).
  • Salt cell needs cleaning.
  • Salt cell needs replacing. As a rule of thumb, salt cells have an average life span of 3 – 4 years here in the Pilbara.
  • Chlorinator needs replacing. Chlorinators can die for a number of reasons:
    – 8 to 12 years old is the average Chlorinator life span.
    – The Power Board or PCB Board (the brains of the Chlorinator) has seized.
    Sometimes it’s better and easier on your back pocket in the long run to replace than fix.
  • If you’re not sporting a Chlorinator (and shame on you), you’re not manually dosing it with enough liquid or granulated chlorine.
  • Your Cyanuric Acid (UV Blockout) level is low, therefore the majority of the chlorine in the water is getting evaporated by the sun.

How to fix it

  • If you’re sporting a Chlorinator, add 1 or 2 bags of salt. Salt should sit around 5000ppm (parts per million). Each 20kg bag of salt equals roughly 500ppm for 60,000L pools, so adding 2 bags will bring your salt level up 1000ppm.
  • Clean your salt cell (remove your salt cell from its housing and give it a hydrochloric acid bath in 10% acid 90% water for 3-5 minutes until the majority of the calcium bubbles up and dissolves).
  • Replace your Chlorinator Salt Cell.
  • Replace your Chlorinator.
  • Use granulated chlorine instead of liquid chlorine and add 1-2 cups – it’s much stronger. Always choose NON-stabilised granulated chlorine.
  • Dose your pool with Cyanuric Acid (UV blockout/stabiliser). Always follow dosing instructions on the back of the package and never add more than 500g-1kg of Cyanuric Acid at a time.

a tub of Stabilised Pool Chlorine pilbara contracting
*We recommend only using stabilised chlorine (featured above) if absolutely necessary. Preferably, you should be using non-stabilised chlorine and adding in your stabiliser separately to avoid a chlorine lock (chlorine locks are explained in the stabiliser section further down this guide). The reason for this is you require much less stabiliser than you do chlorine.

Too high

What does too high mean?

Too much chlorine in the water can be harmful to swimmers and cause skin and eye irritations. Green hair incoming!

Reasons it could be high:

  • Your pool has been over dosed with too much liquid or powder chlorine.
  • Your Chlorinator is turned up too high.
  • Your TOTAL chlorine level is high (and your FREE chlorine is low) but ineffective due to a “chlorine lock”, which happens when too much Cyanuric Acid is added to the pool.

How to fix it?

  • You can get “chlorine remover” chemical if it is urgent. Though, this is expensive and may end up costing you an arm, leg and your first-born. If it’s not urgent, the sun will naturally dissolve excess chlorine within 3-5 days in exposed sunlight.
  • Turn your Chlorinator down to its lowest setting (10-20%) until the chlorine levels balance out.
  • If you’re manually dosing your pool with Liquid Chlorine or Granulated Chlorine, stop adding Chlorine until it is back down to normal range on your test strip. Avoid swimming, or wear goggles if you do.
  • Check Stabiliser (UV Blockout) levels and ensure that levels are a max 30 – 50ppm on your test strip. If higher, caution will need to be taken to remove water from the pool and refill with fresh water.


Too low

What does too low mean?
High pH water corrodes metal surfaces and pool components such as ladders, railings, screws, pool light fixtures, as well as metal surfaces in your pump, filter system, and heater.

Reasons it could be too low:

  • You have added too much hydrochloric acid.
  • You are currently adding excess acid to lower your pH to fix an algae problem in your pool.

How to fix it:
Add Alkalinity Up (sodium bicarbonate/buffer) to the pool with applicable dosage rates to your pool volume. As a general rule 1.75kilos of Alkalinity Up will raise the pH of an average backyard pool of 32 m2, or approximately 42,000 litres of water, by 1.1.

Pool Shop, pool chemicals, pool supplies, Karratha, Pilbara

Too high

What does it mean?
If it isn’t already, your pool will start to turn green soon. Or, you may be having blackspot algae issues. Algae loves high pH. Also, chlorine isn’t as effective when pH is high.

Reason’s it could be high:

  • Your phosphates are high. Phosphates are caused by debris sitting in the bottom of your pool, such as leaves and run-off after a storm.
  • You haven’t dosed your pool with hydrochloric acid for a few months.

How to fix it:

You could use pH down tablets or depending on how bad the issue is you could dose your pool with Hydrochloric Acid. 1-2L of it to start with. Be careful when adding it to make sure it doesn’t splash on you as it is highly toxic and dangerous, and only add 1L every 24 hours if your pool is Vinyl lined as it’s more sensitive to harsh chemicals. pH should sit around 7.5, if you’re having a blackspot algae problem, keep our pH at around 7 for 2-3 months and watch that slowly dissipate.



Too low

What does too low mean?
Water could be quite acidic and causing damage to equipment or etching on pool surface.

Reasons it could be too low:
Incorrect pH balance or frequently back washing.

How to fix it:
Add Alkalinity Up to the pool with applicable dosage rates to your pool volume. As a general rule 1.75kilos of Alkalinity Up will raise the pH of an average backyard pool of 32 m2, or approximately 42,000 litres of water, by 1.1.
Pool Shop, pool chemicals, pool supplies, Karratha, Pilbara

Too high

What does too high mean?
The problem with unbalanced alkalinity levels is mainly how it affects the pH levels, which can result in them being too high.

Reasons it could be too high:
One of the main reasons pool alkalinity can get too high is when you have added too much Alkalinity Up when you were trying to raise it.

How to fix it:
In very rare cases, your total alkalinity may be high but with a low pH in the same pool. If so, using muriatic acid directly to lower Total Alkalinity is not a good idea since this will further lower pH down to very dangerous levels for a swimming pool. For more information, reach out to our Pool team on 9185 3919 or email us at


Too low

What does too low mean?
The sun will be dissolving any chlorine added to your water quicker than usual.

Reasons it could be low:
You haven’t dosed your pool with Cyanuric Acid (UV Blockout) for a few months.

How to fix it:
Dose your pool with Cyanuric Acid. Always follow dosing instructions on the back of package. We recommend adding it in lots of 500g. You can always add more, but can’t take it out if you add too much.

a bag of UV Blockout to stabilise pool sanitisers

Too high

What does this mean?
You could have just added too much stabiliser to your water, and need to give it a break for a couple of months to let it settle back down again.

Worst case scenario is that your water could be in a chlorine lock, meaning that the chlorine level is high but is having no effect on the water.

What does a chlorine lock actually mean?
A “Chlorine Lock” occurs when a pool’s free chlorine (FC) is overpowered by its cyanuric acid (also known as CYA or Stabilizer). Though CYA is vital in stabilizing (hence the name) chlorine for sanitation, too much of it decreases the effectiveness of chlorine.

Put simply, it means that the chlorine in the pool is useless which means the water isn’t being sanitized. It can also indicate the presence of chloramines which give off a chlorine smell.

Chlorine lock isn’t the end of the world, but it is a common problem for swimming pool owners.

Reasons it could be too high:

  • You have dosed your pool with too much Cyanuric Acid.
  • You are frequently using Stabilised granulated chlorine (big no, no). We recommend checking the chlorine that you are using to ensure it is not stabilised.

How to fix it:

Provided that you are in the worst case scenario basket and are experiencing a chlorine lock, the only way to fix a chlorine lock is by emptying the pool and re-filling it. Though, we highly recommend always talking to a pool expert for advice before emptying a pool. For more information, reach out to our Pool team on 9185 3919  or email us at


Salt testers can be expensive (between $200-$400 AUD), so we recommend taking a sample of water down to your local pool shop to get this test. You only need to test for salt 2-3 times a year.

Too low

What does this mean?
Your chlorinator will not have enough salt to produce chlorine to its full capacity.

Reasons it could be low:
You haven’t dosed your water with salt in 6 months or over.

How to fix it:
Add bags of salt to your pool. Your salt level should be sitting at 5000ppm (parts per million). Each 20kg bag of salt equates to 500ppm for an average 60,000L pool. A good starting point is 2 bags if you’re in a situation where you can’t get it tested at a local pool shop.

If you’re unable to get your hands on bags of salt, you’re also able to add this handy Salt Water Boost chemical to tie your pool over.



Last but not least, we want to ensure your pool water is free of organic contaminates, bacteria, viruses and algae while neutralising chlorine odours – this is where Oxy Fresh comes in.
Oxy fresh is the garbage man for your pool, and is a great “final product” to add after your chemical levels are balanced. One sachet of Oxy Fresh doses a pool up to 60,000L, and can be added monthly to keep your pool water in a healthy condition.



We personally always like to recommend keeping an Algaecide on-hand year round for a monthly dosage. If your pool is clear and balanced, an algaecide will do its part in keeping any green, black or mustard algae that may slip through the cracks at bay during a chlorine or pH fluctuation.

a bottle of pool power algaecide useed for swimming pools

We hope this has helped provide you with some handy knowledge on how to test and fix your own pool water! If you have any questions, reach out to our friendly team of pool pro’s on 9185 3919, or shoot us an email at

Happy Swimming and Stay Safe from the team at Pilbara Contracting 🙂