Frequently Asked Questions

Opening a swimming pool, how do I do that, what do I need. Closing a swimming pool, how do I do that and what do I need. Testing Swimming pool water

What chemcials do I need, test kits are they all the same? are Spas the same as swimming pools?



Problem Possible Cause Check / Remedy
Algae growth. Sanitiser level low. Sunlight dissipating sanitiser. High pH reducing sanitiser effectiveness. Not using preventative Algaecide. Ensure sanitiser / cyanuric acid levels are adequate throughout the pool. Reduce pH to recommended range of 7.2 – 7.6, Use maintenance algaecide dose.
Calcium hardness too high / scale formation. Build-up of calcium salts. If mains water has a lower calcium level, dilute the pool. Add a monthly dose of Stain & Scale Inhibitor.
Calcium hardness too low / pool grouting soft or eroding. Soft mains water supply. Increase calcium hardness level to a minimum of 200ppm.
Cloudy water. Build-up of swimmer pollution. Inadequate sanitiser levels. Cyanuric acid too high. Ineffective filtration. Water not ‘balanced’ correctly. Check sanitiser levels and if necessary shock dose the pool. Dilute to reduce cyanuric acid levels. Filter media needs cleaning / changing. Check water balance and adjust if required.
Chlorine level low / difficult to maintain. Lack of sanitiser / cynauric acid. High bather load / prolonged hot weather. Increase sanitiser dose and if necessary adjust cyanuric acid levels. More frequent shock dosing may be required.
Chlorine reading is zero using test kit despite chemical additions. Chlorine level may be too high causing test reagents to bleach. Chlorine demand (very high build-up of pollutants). Allow sanitiser level to drop naturally / lower using Chlorine Reducer or dilute by partially draining and refilling. Continue to shock dose pool water if over-chlorination is not the cause.
Chlorine level is high Over chlorination Allow sanitiser level to drop naturally, lower using Chlorine Reducer or dilute by partially draining & refilling.
Green staining Copper in pool water precipitating Test copper level. Check water balance and adjust if necessary. Add an initial dose of Stain & Scale Inhibitor. For sand filters, also use Aquasparkle Tabs or Flockfix Cartridges to aid with copper removal.
pH level high High pH of mains water. Alkaline shock treatment being used. Regular doses




Seasonal Tasks

Preparing the pool for the winter

At the end of the outdoor swimming season there are a few things that you need to do to prepare the pool for the winter to ensure that the pool and pool equipment are protected from damage and that the water stays in reasonable condition. If you are not confident in winterising the pool yourself then we would recommend that you talk to your Blue Horizons supplier, who in most cases will be pleased to do it for you.

If you are confident that you can winterise the pool yourself then below is a brief outline of some of the things that need to be done.

1. Remove the solar cover, clean it, pack it up carefully and store it away somewhere that mice can't get at it.

2. Check the pH level and raise it to 7.6 – 7.8, this is slightly higher than the normal range and allows for dilution by rainwater (rainwater tends to be acidic) during the closed season.

3. Lower the water level in the pool so it is approximately 150mm – 200mm below the skimmer mouth opening in the pool.

4. Add a 10mg/l shock dose using Blue Horizons Granular Shock, Shock 'n' Floc Granules or Rapid Shock

5. Add Blue Horizons Ultimate Winter Time, Concentrated Winter Time or AlgiMAX Eliminator at the required dose rate, or Kleen Pool.

6. Keep the filtration system running after you have added the above products to ensure they are distributed, to do this you will need to close the valve for the skimmer(s) in the plant room and just draw water via the main drain, otherwise you will suck air into the circulation system.

7. Put bungs into the water outlets at the bottom of the skimmer(s) to stop rainwater going down the pipe.

8. In the plant room open the valve for the skimmer(s) and run the pump for a few seconds only, this will clear the skimmer pipelines of water.

9. Turn the filtration system off.

10. Drain down the pump, filter and heater as per the manufacturer's instructions.

11. Disconnect the pipe-work from the pump, if the plant room is likely to freeze or get damp during the winter it is good practice to remove the pump to a warm, dry place.

12. Float some items in the pool, old chemical containers are ideal for this but weight them first with some small stones so that they are partially submerged under the water. Doing this will take the pressure off the sides of the pool should ice form on the water's surface.

13. Put an old, weighted chemical container in the skimmer(s), this will help relieve the pressure off the skimmer sides – because although the skimmer is empty at the time of winterising it will fill with rainwater over time.

14. Fit your winter debris cover to keep leaves and other debris out of the pool during the closed period.

15. Every 4 – 6 weeks add a 5mg/l dose of Blue Horizons Granular Shock, Shock 'n' Floc Granules or Rapid Shock and brush pool to help distribute the product as best you can.



The Rural Development Programme for England (RDPE) is funded by Defra and the EU. The European Agricultural Fund for Rural Development (EAFRD): Europe investing in rural areas