Spa Decontamination Procedure

I. INTRODUCTION

This procedure is intended to describe how to decontaminate a spa infested with both bacteria and bacterial by-products. Some signs of possible infestation include: slime formation, cloudy water, musty odors, fecal contamination, bather rashes (a rash may take up to 7 days to develop), or flu-like symptoms suspected to have originated from spa use. If the user/operator of the spa suspects infestation, this procedure should be followed as a precaution. If the spa water has become infested with bacteria, the plumbing system and filter may be harboring excessive amounts of bacteria and bacterial by-products. Replacing the spa water is a good practice guidelines on regular water replacement intervals are attached in the Appendix. However, water replacement will not completely eliminate the bacteria from a severely infested spa. The spa and its circulation systems and airlines should be thoroughly decontaminated.

This procedure should be used to decontaminate an infested spa. It may also be used as a general maintenance step when a spa is drained. Three main steps are involved:

1. Draining and decontamination;
2. Water replacement and treatment; and
3. Verification. The verification step is strongly advised for cases where fouling has occurred, but is less crucial when this decontamination procedure is part of a frequent, general water replacement routine.

II. DECONTAMINATION STEPS

A. Decontamination

1. Filters

Cartridge Filters: Remove the filter cartridge and either clean or replace it. To clean a cartridge, first use a filter cleaner as per label directions. After rinsing the cartridge, completely submerge the cartridge in a 1/10 dilution of sodium hypochlorite (liquid bleach) from one to four hours. Inspect and clean the filter housing interior. Install filter grids after spa decontamination is complete.

Diatomaceous Earth (DE) Filters: Backwash the filter thoroughly. Use a filter cleaner as per label directions. Wash the remaining DE from the filter grids. Where possible, remove and submerge filter grids in a 1/10 dilution of sodium hypochlorite (liquid bleach) from one to four hours. Inspect and clean the filter housing interior. Install filter grids after spa decontamination is complete.

Sand Filters: Backwash the filter thoroughly. Remove and dispose of the sand or DE filter media.¹ Check the filter to determine that the filter is not damaged.

2. Raise the water level in the spa to ½ inch above the high water mark.

3. Add at least 100 ppm chlorine to the spa.²

¹ When following the Decontamination Procedure as part of normal spa maintenance, sand replacement may be necessary. Draw down the water to the sand surface and inspect for cracks, mounds or holds. Any of these features can signal a lack of uniform filtration capacity and a need to change the sand.

² For spas treated with a polyhexamethylene biguanide (Biguanide, PHMB) sanitizer, drain and refill the spa prior to adding any chlorine.

4. If possible, cover the spa.

5. Circulate the water at a maximum rate for 30 minutes - 45 minutes and ensure the jets are on maximum.

6. While the water is circulating, turn the aerator (blower) on and off every 5 minutes. Some spas that have air injector (venturi) systems may require the pump to be turned on and off every 5 minutes. This will help ensure that air lines are disinfected.

7. Stop the circulation by turning the jets and aerator off.

8. While the spa is draining, rinse the sides several times.

9. Clean the spa with a surface cleaner, and rinse off surfaces to remove cleaner.

10. Drain the spa to remove any excess water and cleaner.

B. Water Replacement and Treatment

11. Refill the spa with water; replace the filter with a cleaned, sanitized, or new filter cartridge, fresh sand, or DE.

12. Balance the water according to ANSI/NSPI standards.

At this point, the operator may choose to resume normal start-up and maintenance routines according to health-department regulations or ANSI/NSPI standards. Alternatively, a verification step may be carried out to ensure that no excessive sanitizer demand remains.

C. Verification

13. To verify decontamination, shock treat the spa with 10 ppm of chlorine. Allow the spa to circulate overnight or for a period of 8 hours - 12 hours, then check the sanitizer level in the spa. If no free chlorine residual is present, excessive demand may still exist. Repeat the Decontamination Procedure from the first step. Prevent chlorine losses due to sunshine degradation by keeping spa covered and/or carrying out verification step overnight. If two attempts at decontamination fail to produce a chlorine residual, contact your chemical supplier for advice.

14. If residual free chlorine sanitizer is found in #13, proceed with routine maintenance of the spa according to local health department requirements or ANSI/NSPI standards.

15. If after two successive attempts to decontaminate the spa, evidence of contamination persists, a serious problem may exist. Do not resume use of the spa until the problem has been resolved by a qualified professional.

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APPENDIX: WATER REPLACEMENT GUIDELINES

This procedure provides guidelines on how to determine the frequency for which spa or hot tub water should be replaced.

Test the Total Dissolved Solids (TDS) and calculate the Water Replacement Interval (WRI) to determine when your spa needs to be drained. Drain the spa completely, clean it thoroughly, and refill it with source water when either of the following conditions is met:

1. The Total Dissolved Solids (TDS) in the spa water exceeds the source-water TDS by 1,500 ppm or more.

Or

2. The Water Replacement Interval (WRI) is less than or equal to the number of days since the last time the water was drained. WRI is calculated as shown in the formula and examples below.

WRI, days = (1/3) (Spa Volume, U.S. Gallons) / (Number of Bathers/Day)

Example 1

The TDS of the original source water was measured and recorded to be 800 ppm. The TDS of the spa water is now reading 2,500 ppm. The difference is greater than 1,500 ppm (2,500 ppm - 800 ppm = 1,700 ppm) and therefore the spa should be drained immediately.

Example 2

Consider a 600-gallon spa that was last drained and refilled Sunday evening. Each day the operator estimates the number of bathers that used the spa that day and calculates the WRI. This calculated value is then rounded off to yield a whole number. Referring to the table below, the operator would have calculated based on 85 bathers on Monday:

Water Replacement Interval, days = (1/3) x 600 / 85 = 200 / 85 = 2.4 or about 2 days

The spa water was replaced Tuesday evening because the Monday bather load (85) dictated that a two-day WRI was required.

Example 3
Referring to the table above, the WRI values for Wednesday and Thursday did not indicate a need to drain the spa. The water was replaced on Friday evening because the Friday bather load (105) dictated a two-day WRI (Friday is already three days after Tuesday).

Example 4
The water was replaced again Sunday evening because of the Saturday bather load (100). The bather load on Sunday was irrelevant because the spa would be drained regardless due to the high bather load on Saturday.

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