Rubbermaid 10 gal. Mash Tun

I'm using a 10 gal Rubbermaid cooler with SS false bottom. I've never had what could be described as a 'plastic' taste. Could be a flaw in your process. Chlorine based sanitizers are frequently associated with a Band-Aid type flavor in beer if not rinsed thoroughly. Even Chlorinated tap water could be to blame. Have you ruled that out?

 

Another thing that might cause that taste is chloramines in the water (they don't boil out).

I used my cooler mash tun on the first try with zero plastic taste at all. If it's meant for water, I wouldn't immediately suspect the cooler as leaving a plasticy taste, but I suppose it's possible.

 

I use a similar set up and never experienced this problem. How was your fermentation and did you use a starter?

 

What water did you use?

 

OP, as the others have said, it definitely sounds like a chlorine / chloramine problem. As a new homebrewer with only 5 batches on my belt, this was an issue I just most recently overcame. All my beers were good, but there was a "band-aid" flavor in the background that kept bothering me. I overcame the problem by using RO water.

From John Palmer's How to Brew (recently pointed out to me by another helpful BA):
"Some city water supplies use a chemical called chloramine instead of chlorine to kill bacteria. Chloramine cannot be removed by boiling and will give a medicinal taste to beer. Chloramine can be removed by running the water through an activated-charcoal filter, or by adding a campden tablet (potassium metabisulfite)."

 

In addition to using a campden tablet or metabisulfite, I believe Vitamin C or Citric Acid can also be used. This can be done by simply crushing up a Vitamin C tablet and dissolving into your strike water before heating it up.

 

I used to have odd tastes in my brews. Finally narrowed it down to my water. First handful of brews used water from house I was living in with a water softener (Big NO NO), then in another apt. straight tap water. I now have 3 5 gallon water jugs that I fill with R.O. water at walmart or Meijer's when I go grocery shopping @ 0.39 a gallon. Depending on the beer I'm brewing, I then add mineral's back into it via Gypsum, Calcium Chloride, and Epsom Salt to the desired levels. Since doing this my beers have been on point. I'd look at your water, not the cooler.