Residential Pools and Spas

Advice on cleaning up after the floods

February 7, 2011
Floods covered three-quarters of Queensland

Bill Mansfield from BioGuard, Steven Humphris from Focus and Paul Simons from Lo-Chlor have offered some advice to help pool professionals clean up after the floods.

Advice from BioGuard
Bill Mansfield, Education Officer at BioGuard has suggested that pool service technicians and pool owners need to realise that a pool that “looks” dirty might not be much of a health problem – but a pool that has been contaminated by sewage can be a serious health risk.

To make sure your pool is healthy after a flooding with potential contaminants, you must maintain a very high free chlorine level for approximately half a day with the filter and pump operating. Check your local state and council regulation for the precise measurements of how high you should dose your pool.

Mansfield offers some simple instructions for cleaning a flooded pool.
• Remove all solid wastes (leaves, branches, rubbish);
• Check equipment, there is no need to add chemicals if the mechanics are not working (filter and pump).
In the worst case scenario – if there has been a danger of sewage contamination – the pool will need to be thoroughly disinfected.
The safest way to be sure of killing the pathogens caused from serious contaminations is to increase the dosages of chlorine for a longer than normal period of time. It is called the CT value or ‘concentration time’, concentration of free chlorine (mg/L) x time (minutes).
The State you are in will determine the CT value you should achieve for your pool. On average the cleanup requires a CT value above 10,000.
The calculations for CT values work like this:
20mg/L (free chlorine) for 12 hours
20 x (12 hours = 720 minutes)
20 x 720 = CT value of 14,400
The required CT values vary by State. Mansfield offers the following information regarding State regulations for faecal cleanup.
NSW: CT value above 15,300;
VIC: CT value of approximately 10,000;
QLD: Shock dose the pool overnight (no specific regulations on CT values);
SA: Super disinfect the contaminated area.
After you have sanitised your pool again, you can begin the cleanup. Even if you drain the pool, there may be bacteria that survive in the pipes and filter, so draining is not the solution if you are unsure if your pool is contaminated.
Draining might also be impractical for a number of reasons including the danger of the pool popping out of the ground because of hydrostatic pressure.
Mansfield offers the following cleanup method:
1. Check mechanical equipment for damage;
2. Remove large debris;
3. Floc pool;
4. Vacuum to waste;
5. Leave pump/filter on till you have balanced the pool;
6. Test for metals and treat accordingly;
7. Test for Chlorine Demand and treat accordingly;
8. Use algaecide;
9. Manage chlorine residual with optimiser;
10. Use clarifier;
11. Manage water balance;
12. Use clarifier.
Follow label instructions for application of all products.
Advice from Focus
Steven Humphris from Focus says that any pool that has had contaminated river run-off mix with the pool water, should be totally drained, cleaned, then re-filled with fresh town water. No pool should be simply treated with a flocculent, cleaned and re-balanced if contaminated flood water is present as this can be a major health risk.
Caution needs to be taken when draining pools at this time as the flood water has made ground conditions around the foundations of the pool very wet. Pools should not be drained until ground conditions have dried to at least the  depth of the pool as the entire shell of the pool (fibreglass or concrete) can “pop” out of its original position with the change in hydrostatic pressures.
Until such time that the pool can be drained, Focus is advising pool technicians to dose the pools contaminated with these flood waters with a large amount of chlorine and wait until they are happy that the ground has dried up sufficiently to avoid these complications. Some pools are requiring in excess of 40kg of Calcium Hypochlorite before a chlorine reading has been obtained. If a pool owner insists on having the pool drained, cleaned and balanced straight away, Focus would recommend having the owner sign a disclaimer to make them aware of the potential risks. All electrical pool equipment needs to be checked by a licensed electrician or replaced before the pool is re-commissioned.
For those businesses experiencing a shortage of salt or liquid chlorine in this busy period, Focus has put together an alternate sanitation program to assist customers maintain a safe, sanitised, clear pool without the hassle of adding a daily sanitiser.
The salt pool owners should be advised that running a low salt level may void their manufacturer warranty on the salt chlorinator. For more information call 1300 136 287.
Advice from LoChlor
Paul Simons from Lo-Chlor has also offered advice on how manage flood affected swimming pools.
He says that the first thing to be done with any pool that has been submerged is to dump the water and refill the pool – being sure to take into account the danger of the pool popping out because of hydrostatic pressure.
However, even after refilling the pool, the water will still be a mess because of the existing water in the lines. So there will still be the need for a regime of heavy dosing to get the water back to normal.
“Normally when you have an extremely cloudy pool the pH and TAL (Total Alkalinity) tend to be very high,” he says. “In the case of the Queensland floods (due to the high soil content and the low pH of soil) the pH and the TAL of the water will be quite low. Low pH in particular tends to hamper the effects of flocculants and clarifying agents when clearing a mud slide in a pool. These products (flocculants in particular) require a higher than normal pH for them to be effective.”


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