Soapy off-flavour source?

My last malt extract batch of red ale has very similar "soapy" off flavor. The beer is still very drinkable and I do enjoy it but that bitter/soapy after taste is there. I at first just thought it was a hoppy taste but this is not a hoppy beer so that may not be the case. I feel confident that it is not a real "soap" taste. I use one-step for a cleanser and star san for my sanitizer and don't rinse either but all the research I have done on this tells me it shouldn't produce any off flavors. I said all of that to say this... I used tap water with no additives and our tap water has a very high chlorine taste out of the faucet, so my batch that is fermenting now I used a brita charcoal filter on the tap to try to eliminate that. If chlorine isn't the culprit, I really think it is the yeast. I'd appreciate any other opinions as well. Cheers!

It could be the hops. Were they all IPAs?

I have heard people say that long dry hopping can cause soapy flavors. This happened to a home brewer I know on his first IPA. He said it tasted soapy. He let it sit in the fridge for a few weeks and it was gone.

I found a guy here at work thinks the Founders Centennial IPA that we are all drinking tastes like "detergent". I don't think that is an off flavor. It's the flavor of the hops at copious quantities. It's a strong flavor. I think "hops" and he things "detergent".

I've come across soapy flavors on a handful of occasions, and I've yet to figure out where exactly they come from.

My sources indicate that soapy flavors can come from either various salts, or various esters and organic acids. This leads me to believe that water and fermentation conditions and/or yeast strain/health all can lead to conditions which result in this flavor in one way or another.

Salts: Magnesium/calcium/potassium chloride, Sodium sulfate/carbonate

Esters: Ethyl dodecanoate, ethyl tridecanoate

Acids: Capric acid, dodecanoic acid, pyroglutamic acid

When brewing extract, I'd sometimes found that the extract in contact with the tin sometimes tasted soapy. The taste left a very long lasting back of the tongue bitterness, a bit like eating soap bubbles in the bath (surely everyone has done this as a kid?)

I used to use boiling water to loosen the extract from the inner side and completely empty the tin, but stopped doing that after noticing the off flavour, which did make it though the final beer.

This may help: From John Palmer's How to Brew:

Soapy flavors can caused by not washing your glass very well, but they can also be produced by the fermentation conditions. If you leave the beer in the primary fermentor for a relatively long period of time after primary fermentation is over ("long" depends on the style and other fermentation factors), soapy flavors can result from the breakdown of fatty acids in the trub. Soap is, by definition, the salt of a fatty acid; so you are literally tasting soap.

http://www.howtobrew.com/section4/chapter21-2.html

I found this while reading Brewing Classic Styles by Jamil Zainasheff:

If your water is highly alkaline, the beer pH may be too high, causing the beer to taste dull, soapy, or excessively bitter.

(emphasis mine)

Have you checked your local water report?

How long do you leave your beer in primary? It's possible that you are leaving it too long on the trub, which can cause soapy flavors due to breakdown of fatty acids in the trub.

My other guess is that it has something to do with your sanitizer and not cleaning your equipment properly.