When a swimming pool has been inundated with floodwater there are many issues that need to be considered. It is not essential that a swimming pool be restored immediately but it is essential to assess the condition of the swimming pool and make it safe before starting any work. An unused swimming pool is not likely to transmit, or become a source of, diseases in the short term unless sewage has contaminated the pool.
Once the floodwaters have receded the swimming pool needs to be assessed to determine that the fencing is intact to prevent children from accidental drowning. Check any pump house and other structures to ensure that snakes, spiders or other pests are not a threat. Reptiles and insects that appear to be dead may still be alive. Secure or restrict access to the area if possible, particularly if fences have been damaged or debris has made the area dangerous. The local council should be able to provide advice on swimming pool fencing requirements.
If the swimming pool, pump, timer and any electrical equipment have been fully inundated, once the floodwater has receded a licensed electrician should check the circuits and each electrical fitting to ensure electrical integrity. This may need to be done in consultation with the local pool shop in case electrical components need to be replaced.
Severe damage may mean that the pool area should be secured, made safe and/or abandoned until a consultant (or insurance assessor) is able to give professional advice. Do not pump out a swimming pool immediately as this may cause more structural damage than leaving the pool full. An empty pool, particularly a fibreglass pool, may pop out of the ground. Check the pool surrounds for wash outs, missing paving materials or deposited debris. Eventually the pool may need to be pumped/cleaned out to allow a full assessment of the damage.
While the pool is full but not able to be restored it may promote mosquito breeding and should be checked daily. If mosquito breeding is detected then 1 cup of household kerosene should be added to the pool water weekly. If the pool starts to turn green then an algal bloom is developing. A local swimming pool shop should be consulted to determine the best practice to minimise the algal bloom.
The contents of the pool need to be assessed. If the pool has received silt or other soil material during the flood it may need to be pumped or bucketed out. There may be unusual material washed into the pool that could be hazardous as well as affecting the pool water quality. The local council needs to be consulted as to where the pool contents may be discharged. It is not appropriate to pump out the pool to the sewer.
The water is likely to be very dirty and any attempt to filter the water will rapidly clog the filter. Consult a pool shop on how to "flocculate" the pool water to precipitate and remove the suspended colloidal soil material. The flocculated material should be vacuumed to waste and not filtered. Once the pool has been flocculated the pool filter can be turned back on to circulate and filter the water. Sufficient (check the label) liquid chlorine (sodium hypochlorite) should be gradually added to the pool to raise the free chlorine concentration to 5 mg/L and the pH to 7.2 at least overnight with the filter running. Once this has been achieved normal pool operation can be re-instated. If salt water chlorination is used then the salt concentration should be then adjusted.
For further information contact your pool shop or local public health unit.