Pool Leaks

Help! My Pool’s leaking!leaking pipe

We get dozens of calls like this every year and the good news for the beleaguered pool-owner is that most suspected leaks turn out not to be leaks at all

Leaks are not uncommon but happily there is quite a lot you can do to diagnose the water-loss for yourself (DIY) without incurring an unnecessary call-out fee

The commonest leak is from the Rotary Valve gasket: -  

  • Check for a trickle of water whilst the pump is running 
  • Undo the screw-in sight glass jar on the Rotary Valve or simply check the far end of the waste pipe where it meets the drains
  • A steady drip from a worn Rotary Valve gasket can cost you a lot of water in a season - it’s much cheaper to replace the gasket or Rotary Valve, or to install a valve on the waste pipe
  • Keep the Waste Valve closed at all times unless you are back-washing, rinsing the filter or draining your pool
  • That way, even if the Rotary Valve gasket is leaking, no water can be lost to the drains


A hot summer day, coupled with a breeze across the surface of the pool, can easily evaporate 25mm (1”) of water in 24 hours so you need to make sure that your reduced water level is not due to evaporation

(The solution to excess evaporation of pool-water is to fit a pool-cover. You will also benefit from a longer swimming season and a cleaner pool - and a pool that needs less of those expensive chemicals to keep it sanitized)

Here's how to check if your 'leak' is really down to evaporation: -

  • Half-fill a plastic or rubber (non-metallic) container with pool water and put a brick or some similar heavy object in the bottom
  • Mark the waterline on the inside of the container
  • Stand the container at the side of the pool in a place where it will receive full sunlight all day
  • Mark the pool wall or steps at the waterline - use a pencil for this - and leave the pool unused for a day or two
  • Check the water levels
  • If both levels have gone down by the same amount the loss is due to evaporationDog drinking from bucket
  • If the pool level has gone down more than the bucket you may have a leak
  • This method works for both indoor and outdoor pools, and it doesn't matter if it rains
  • If the bucket level has gone down more than the pool level it means that your dog has been drinking out of the bucket. . . .

If you still think you have a leak - carry out further testing

  • Measure the water loss with the pump/filter on for 24 hours and note the result
  • Next, measure the water loss with the pump off for 24 hours and note the result
  • If the leak is faster when the pump is running the leak is on the pressure side of the circulation system - i.e. between the pump and the return jets
  • A sure indicator that this is the case is if you get a small amount of soil washed into the pool from the jets when the pump first starts up
  • If the leak gets worse when the pump is off, it is likely that the leak is somewhere on the suction side of the system – i.e. between the skimmers/bottom drain/vacuum socket and the pump
  • If there is no change in the rate of leakage it's more likely that the leak is somewhere in the pool shell
  • If you think you have a leak on the pressure side of the circulation system, and you have a vinyl liner, check that water is not getting behind the liner at the return-inlet fittings because if the gasket is damaged, water can sometimes get past and behind the liner


If tests indicate that there may be a leak on the pipe-work, you’ll need to get a leak-detection expert in to pressure-test the system to discover where the leak is

Some companies trace leaks with electronic equipment and whilst they may appear to be expensive they can save time and work by identifying the exact point of leakage

It is necessary to dig for and expose the pipe to repair the defects; so pinpointing the exact spot may be cheaper in the long run


If you think that the leak is somewhere on the shell

Whether it’s a liner, PVC or a concrete pool, it is often best to simply check and adjust pH, and then Superchlorinate, turn off the circulation system, and let the water level keep falling until it stops

When the water stops falling; the leak is likely to be somewhere along the level of the current waterline

If the water level cuts across a pool fitting (Jet, Skimmer, Vacuum Point, light fitting, etc.), - that fitting is immediately your main suspect but if the pool has a vinyl liner you will need to carefully check the liner all along the final water line for tiny holes

An inexpensive leak-tracing stain liquid can be made from a plastic drinks bottle, the type that has a nozzle on the cap, filled with tap-water mixed with writing ink or food colouring

  • Gently squeeze a small quantity of the liquid in the close vicinity of the suspected fitting, visible crack or damaged liner
  • If there is a leak in this area you will observe the stain liquid being drawn away by the current
  • There is no permanent staining of the water when using this leak-finding stain because the chlorine bleaches it out almost immediately

Incidentally, there are now several products for sealing leaks in pools

They are not cheap but are very effective for small to medium leaks and definitely MUCH, MUCH cheaper that calling in a leak-detection company to find your leak, then digging the terrace up to repair it.

We import the very best of them - Fix-a-Leak - from Canada and supply it in Spain on Amazon.es or by prior arrangement from our store in Alhaurin el Grande. Remember to call first, please.

See https://www.amazon.es/dp/B017B00LEQ for online supply.

Follow the instructions very carefully and ensure that the Rotary Valve is set to ‘Recirculate’ when the product is applied

Failure to  set to ‘Recirculate’  will mean that all the channels in the filter will be sealed up; yes, it really is that good!


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Note: - Please contact our recommended pool professionals for supply and installation of all pool-related services: - 

Andalusia and the Costa del Sol - Pool Safety SpainPool Safety Spain

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*We only offer Quotations: - a fixed, agreed price that cannot, and will not, be increased. We do not give 'estimates', as an estimate offers the client no guarantee of final price

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Ken Walker - MyPoolGuru©