TimelineDate __________ Action

+0 hours

Faecal incident, close the pool immediately

0 hours 5 minutes

Increase flocculent (APF) application level to 2 ml per cubic metre of water filtered per hour. If pool flow is 120 cubm/hr, flocculent application rate should be 240 ml/hr.


Increase free chlorine level to 3 mg/l


start as soon as possible, scoop out as much solid material and vacuum up any visible material, the whole pool floor and surrounds should be cleaned. This task should be completed within 4 hours. Do not use any cleaning agent that contains surfactants. Sodium bicarbonate solution is acceptable.

+ 4 hours

Four hours after the faecal incident, back-wash the filters for a minimum of 5 minutes at >40m/hr for AFM or >55m/hr for sand. After the back-wash, rinse the filters and then go on-line with the pool water.


Take a water sample of the back-wash water in a 1.0 litre clean plastic container 1 minute after the start of the back-wash, and store in a fridge, the sample may be used for DNA crypto analysis.

+4 hours 30minutes

Maintain the chlorine level at 3 mg/l, maintain the flocculation dosing at 2 ml/m3


Isolate your pH, redox and chlorine probes from the system water, and manually check the free chlorine level, adjust to a concentration between 3mg/l  and 4mg/l


Add DryOx, 4 x tabs per 20 cubm of water, or raise the chlorine dioxide level to at least 0.4mg/l. The tabs should be added directly to the pool water.


Continue to recycle the water for the following 12 hours, measure the free chlorine level every 2 hours and maintain above 3mg/l

+16 hours

Repeat the back-wash procedure, and take a second   1 litre sample of back-wash water, 1 minute after starting


Bring your pH, redox and chlorine probes back-on-line. The DryOx tabs can give a false high reading, so calibrate the instrument reading to the manual reading.


Operate for the following 4 hours at 3mg/l, dosing 2 ml/m3 of (AFM)  flocculent using a peristaltic pump.

+20 hours

Stop adding chlorine and monitor the chlorine levels in the system every hour. If there is no change to the chlorine level, or if it does not change by more than 20% over the 4 hour period then this may be deemed acceptable.


reduce flocculation (APF)  dosing to 1 ml/m3 of water passed through the filters.

+24 hours

Final water quality parameters should be as follows;

a. Turbidity <0.05 ntu

b. RLU (ATP) < 50 as measured by 3M unit, or the equivalent by an alternative manufacturer. Measurements to be taken in the pool water. Also test a sample immediately before and after the filters.

c. All other water quality parameters to be in compliance with your countries standard, or the PAWS standard

+24 hours

If all water quality parameters are in compliance, you may consider opening the pool to the public, but we would recommend a full bacteriological and cryptosporidium analysis of the water by an independent certified laboratory for verification prior to opening to the public.

+7 days

Cryptosporidium oocysts, and other organisms may still be present in the system. We therefore recommend a prophylactic treatment with DryOx, 1 x tab per 20cubm of water added 15 minutes prior to the next filter back-wash

Additional notes.

a. Flocculation dose rates may vary depending upon the product, APF is a proprietary product of Dryden Aqua. click here for information. Under no circumstance should pools be operated without proper flocculation.

b. DryOx is a proprietary product of Dryden Aqua, click here for information

c. There may be insufficient water to back-wash twice in 24 hours. If this is the case the pool should remain closed until the filters can be back-wash twice and then operated for a further 8 hours after a back-wash to allow the filters to stabilize.

d. Action plan relates to UK guidelines under the PAWS standard, different procedures may be required in different countries.

e. There should be an 8 hour period between back-washing the filters or water flows disruption, during normal operation, and most especially for at least a 2 week period after a faecal incident.

f. The above procedure applies to well design systems or pools in compliance to the German DIN standards. It may not be possible to follow the above procedures unless the filters can mechanically cope with the flow rates and pressures, also systems without a rinse facility will be deficient and may require extra attention to clear the system of possible infection.

g. Pools operating with high rate filters above 30m/hr, should raise free chlorine to 50mg/l, add DryOx, recycle for 5 hours, neutralize the chlorine dump all the water. Clean and rinse all surfaces, wash with DryOx solution and then refill.

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