How to Clean a Wine Tank

By: Tom Payette, Winemaking Consultant

Cleaning in the winery is one of the most important tasks the winemaker has the most control over in the cellar.  It is often said, and very nearly true, winemaking is 95% cleaning.  Data is shy when it comes to how to clean certain parts of the operation; yet, here is a step by step process of how to clean a stainless steel wine tank in the cellar.  Please keep in mind every cellar visited may have some conditions that may need to have this plan adjusted.

Chemistry

  There is some chemistry to cleaning a wine tank that will be addressed briefly to have an understanding of what one would like to achieve.  Simply put, one must have physical cleanliness first.  This is the removal of all solid particles from the tank’s interior surface(s).  Examples of these items may be seeds, skins, spent yeast, bentonite and so on.  This may not include tartrate removal because this can be assisted chemically if desired.  Once the solids are removed, the tank cleaning person will use a high pH cleaning material to remove the tartrates and to clean the surface of the stainless steel.  This high pH will not only remove tartrates but also kill and eliminate a broad range of wine spoilage microorganisms.  Once this high pH operation is completed, the operator will always come back with a light citric acid rinse to neutralize the high pH cleaner and to have some limited killing power due to this solution’s low pH value.

Items Needed

All safety material to include but not be limited to:

•    Safety goggles

•    Rubber gloves

•    Rubber boots

•    Hat and/or rain gear

•    Procedure

•    Eyewash station or portable eyewash

•    A light citric and water solution close by (roughly 2 tbsp per gallon)

Other items needed will include:

•    Pump that will handle hot water and the chemicals desired to be used.

•    Hoses that are food grade and will stand up to heat and all chemicals used.

•    pH meter (optional but the winery really should have one anyway)

•    High pH cleaner – such as Soda Ash

•    Low pH cleaner – such as Citric Acid

•    Material Safety Data Sheets (MSDS) – on all chemicals used.

•    Flashlight(s)

•    Cover for the tank such as a shower curtain, towel, bed sheet.

•    Distribution system such as a spray ball or tank cleaning “T”

Preparation

  If the winery’s tanks are equipped with automatic solenoids on the tanks, be sure to override the chilling system or to generally isolate the tank to be cleaned so the chilling system will not engage to cool the hot water that will be added to the tank.  Overriding the system may be done by moving the temperature dial setting all the way up so the solenoid will not engage, thus preventing cooling from circulating through the tanks jackets.  Shutting the tank cooling jacket system down may be achieved by simply shutting a valve on the supply side of the tank cooling system jacket, once again disrupting cooling from entering the jackets.

  Allow any ice to fall off the exterior/interior of the wine tank jacket so that it will not fall on the operator, other staff or persons or any equipment used to clean the tanks.

  Rinse the tank and physically remove all of the solids possible.

Procedure

  Once the tank is free of all solids, the chilling is turned off and the tank has deiced, if applicable, one may start the cleaning process.

1.     Apply all safety gear necessary to be safe while doing the tasks described.  This is an internal winery decision that the winery will need to address.

2.     Disassemble the tank of all valves, fittings and gaskets that may be easy to remove.  Rinse these parts with fresh water first then soak them in a high pH solution to help with the cleaning process.  Remove the doors unless these are needed to prevent splashing of the cleaning solutions outside of the tank.  In this case, close the doors loosely to allow the cleaning solution to cover all parts of the door.

3.     Take a brush and clean all of these orifices thoroughly.  Inspect them to make sure they are free of solid debris.  Be certain if any threads exist, a microbial hazard in itself, that these threads are cleaned using a brush or a toothbrush.  Be careful since many tanks have sharp threads that will lacerate one’s skin easily.  Use a brush to remove any other hardened dirty areas on the exterior of the tank.

4.     Inspect the tank visually to see if any solids remain in the tank and rinse them from the tank.

5.     Set up the pump with hoses in a strategic area that will not interfere with any part of the tank cleaning process.  This area could include away from the front of the tank should a ladder need to be placed in that workspace or away from an opening in the tank where water and chemicals could splash/slosh out onto this piece of electrical equipment.

6.     Fill the tank with enough water that one may be able to circulate the water from the bottom port/valve of the tank to the top of the tank with ample extra so that the water will not deplete itself.  This amount could be near 70 gallons for a 3000-gallon tank or less depending on the tank’s configuration.  If the tank has a conical bottom one may need to avoid a vortex.  To combat a vortex, one may place a 5 gallon food grade plastic or stainless steel bucket or two inside the tank.  These will break the development of the vortex.  Be careful they do not clog the outlet of the tank supplying the pump.  Hot water is recommended but not an absolute for tank cleaning.

7.     Attach the suction side of the circulation setup to the bottom valve with a hose.

8.     Attach another set of hose to go to the top of the tank.  This piece should be placed were it will strategically spray water back toward the top of the tank to give maximum distribution of the water and/or cleaning solution.

9.     Cover the top opening with a sheet or towel to prevent splashing of the cleaning water outside of the tank’s opening.

10.  Open the bottom valve and allow the water to circulate to prove to the operator that this action will work as desired.  Look for splashing hazards one may want to avoid if this solution were to contain a cleaning chemical.  Always play with water first!

11.  Once comfortable with the mechanical portion of this process and the operator feels comfortable, one may turn the pump off.

12.  Open the side door and make a cleaning solution to clean the tank.  This is very dependent upon the size of the tank and the amount of potential tartrates that may be present.  To make the cleaning solution, always dissolve the powdered cleaning solution in a bucket before placing into the tank.  (This is done to make sure no caking of the solution may happen.  The solution should be fully and carefully made into a liquid.)

13.  As soon as the cleaning solution is made in the bucket, be sure to add the solution to the wine tank, shut the side door and start the circulation.  Step back from the tank just in case the cleaning solution should want to splash; yet, be able to operate the pump to shut the operation down if needed.  Observe the operation from a distance and listen to make sure the process is working as designed.  Look for open valves to show signs of the cleaning solution and any other areas.

14.  Continue to monitor the process from a distance and always keep your ears on the operation.  The sound of a tank cleaning can be just as important as visually watching the operation.

15.  One can let this process go on for 20-30 minutes or more depending on other operations in the cellar.  The author likes to start the tank cleaning process while working on other projects as long as each process can be monitored properly.  The time is largely affected by the size of the tank and only experience will help the cellar crew in this estimation.

16.  Once the process has been allowed to work, one may turn off the pump and wait 4-5 minutes for the extra dripping of the cleaning solution to cease.

11.  One may carefully open the door. With safety goggles on and a flashlight in hand – one may inspect the tank to see if the process was effective.  Look for areas or patches of tartrates that may not have been dissolved or other areas visually not looking clean.  Take appropriate actions to correct any of these.

18.  Feel the cleaning solution or take a pH reading.  Is the pH still high and does it still feel slippery?

19.  Once one deems the tank to be clean, one can dispose of the spent cleaning solution in the proper manner.

20.  Rinse the tank and empty all hoses of the cleaning solution.  If a bucket was placed in the tank to prevent the vortex – remember to empty its contents.

21.  Add fresh water back to the tank to circulate one more time.

22.  To this water add enough citric acid to get the water at a low pH – perhaps 7 cups into 60 gallons. (Dissolve in water first, as always)

23.  Circulate this solution to contact all parts of the tank the high pH cleaner contacted.  This will neutralize any places back to a reasonable pH level.  This circulation may only take about 5 minutes versus the previous step.

24.  Once finished, open the tank door and feel the water.  It should not be slippery. Run a pH.  The pH should be below 5.5.  If not – ad more citric.

25.  Allow this spent water to drain from the tank and dispose of properly.

26.  Break down the circulation system or move it to another tank.

27.  Rinse the tank one more time with fresh water.

28.  Inspect the tank one more time after the cleaning and make sure to remove the bucket or other tools used in the vortex preventions.

29.  Take the fittings out of the soaking tub and give them a light citric rinse or do this when appropriate and on your timeline.

30.  Always inspect the tank again before filling with wine or juice.

31.  Always look at and smell all the fittings before reinstalling on the tank.  Fittings that smell bad more than likely have bad microbes in them.

32.  Remember to reengage the chilling to that tank so it is ready.

33.  Label the tank cleaned, the date and by whom so others will know what the last process with that tank was.

Summary

  Tank cleaning is extremely important.  It can be done easily just after the tank has been emptied.  The author reports better progress and success with tartrate removal especially if the tank is cleaned within two hours of emptying.  Set your tank cleaning system up to be as easy as possible and make sure the cellar staff is keenly aware of your expectations.  Tanks that are not cleaned properly should not be used and instructions to clean them again would be prudent.  Remember, wine is a product that you and others will drink.  Use tanks that are cleaned with the same amount of dignity that you want your beverages prepared in.

Helpful Hints

  It is not recommended to enter the tank to do any of these processes.  If tank entry is needed, that could require a completely different set up for safety reasons.

  Crack doors and valves to allow the cleaning solutions to coat all areas.  Try these areas first with water and then perform this action with the cleaning solution added.  Remove all gaskets, where appropriate, to allow cleaning them.

  Always check on the interior of the tanks temperature probes and inside manway doors to make sure all is clean, both above and below them.

  Try to have two people around at all times just in case.

  If a certain tank orifice has trouble getting clean try and place a brush or rag in the orifice to absorb the cleaning material so it will “wick” to the upper areas of the orifice.  Then clean the area again physically, rinse the brush or rag and replace for the low pH rinse portion of the cleaning.

  Have a bucket of a light citric solution close by to have access to neutralize any high pH cleaners.

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