this is work related so i'll indulge myself with another post.

there are 3 common sanitizers in the food industry that would also be 
applicable to sanitizing our water holding tanks.  the first and 
fore-most point is that none of these will work unless the tank is 
clean, meaning free of sludge, sediment, guck, pump labels (oh yes, 
mine came off in a big way) and other assorted biofilms.  clean means 
removing the cover and scrubbing the tank with a mild, non-abrasive 
cleanser and pad combo.  i would reccomend the 3M dish washing pads 
that have a pink sponge on one side and a *white* scrubby pad on the 
other.  you do not want to scratch the plastic in cleaning as this 
would give a nice home for bacteria to hide in.  get the tank clean 
and white, period.

THEN you think about sanitizing it.

1.  chlorine compounds.  best on to use is bleach as its cheap and 
available.  yes it is corrosive and will do nasty things to pump 
parts and water level guages if used indiscriminantly.  BUT it is 
safe, cheap and works.  you want to achieve an effective 
concentration of 50 parts per million chlorine for sanitizing.  this 
works out to about 1 tablespoon bleach per gallon.  let it sit in the 
tank half an hour and dump it out.  rinse it out a little with fresh 
water and you're on your way.

2. Quaternary Ammonium products.  there are a variety of products 
available in food service catalogs that utilize this active 
ingrediant for sanitizing.  it also works and has the advantage of 
being non-corrosive BUT it is hard to get, expensive and has a really 
long chemical name that would scare most cockroaches.  mix to an 
effective concentration of 200 ppm.

3. iodine compounds.  again, non-corrosive and to use you want to 
reach an effective concentration of 12.5 ppm.  this means you mix it 
up with water to the color of Dos Equis beer.  it will turn 
polyethylene brown.  if you spill it on your Westy cabinets it will 
leave a rude brown stain. it will stain your fingers a rude brown.  
and it ain't so cheap.

here's my personal recommendation, soley my opinion.  clean your tank 
well, you should need to do this only once. then sanitize with bleach 
at a tablespoon per gallon. i don't worry about corrosion at these 
concentrations and contact time.   after your trip, take the water tank lid 
off and put a piece of cloth over the hole secured with a rubber 
band.  this will let the tank dry out and nasties won't grow.  next 
time you use it you may not even need to sanitize.

chemical test papers that show the effective concentration of these 
sanitizers are available from restaurant supply houses, but you 
really don't need them.

-dan

Daniel Houg
Minnesota Department of Health
Internet Address:  fairwind@northernnet.com
Fax #:  218/755-3823