Help with Off Flavors

I've been brewing for years and seem to be having a recent problem with off flavors. I believe the problem maybe coming from oxidation. It is an astringent flavor in the beer. Here's my operation:
All glass carboy fermenters.
I add oxygen when I pitch the yeast.
I rack out to a secondary after 3-5 days through a 1/2 inch tube into another carboy.
When fermentation is finished I rack to a bottling bucket, add sugar and bottle.
This has been my procedure for years I don't know what has changed. The last 4 to 5 batches have been off.
Does anyone have any suggestions for controlling oxidation or any other suggestions?
Thanks

Has your water source changed?

I'm thinking your water may be getting a heavy dose of chlorine or similar treatment. First thing, I would call the water treatment plant and see if they are doing something different. I know around where I live, they supercharge the river water with chlorine because of heavy rains stirring things up.

Do you do AG or extract?

Any of your procedures different during mash (if AG) or the boil?

Barring wild yeast etc...

If your water PH has changed or the amounts of sufate, magnesium or iron have increased this can casue astringency.

I think I have a slight problem with excess iron recently. And I've been noticing a slight astringency in some of my lower bodied beers. Increasing body with some carpils (ag) or adding some mato-dextrin will help mask this. Your tounge is more perceptive of astringecy with lower bodied beers.

My local water anlysis does not list Iron. Odd.

How about your tubing? Have you cleaned them lately?

Some good questions but I'm not sure we've found the answer.
I always buy Deer park spring water for my beer. I guess it maybe possible that they have changed the water.
My tubing is fairly new and I clean and sanitize it before use.
I mainly use extract with specialty grains.
As far as the water goes, what would you suggest I use to treat it?
Thanks for everyone's input.

Boiling grains too long, bring out tannins? (tea drinkers say not to subject tea to boil for that reason) Enameled brew pot with a chipped spot gone to rust?

look into your sanitizing procedure. do you rinse the sanitizing solution out of everything. barring the water (which weve done) i'd say its probably due to your sanitizing procedure.

Thanks to everyone for the advice. I first thing I'm going to try is something with the grains. My last few batches have been darker beers, stouts, Scottish, Holiday beer. I read on another board that the darker grains should not be in as long.

Darker ales = more specialty grains = more tannins. Get some pH 5.2 and use it in the steeping water. This will help keep the tannins from dissolving. I started using 5.2 to improve AG efficiency and noticed a reduction in astringency.

If your are looking at a water analysis from your local company, they only test for chemicals and minerals considered dangerous. Iron and calcium (our main concerns) aren't checked.

david_42 said:

If your are looking at a water analysis from your local company, they only test for chemicals and minerals considered dangerous. Iron and calcium (our main concerns) aren't checked.

Click to expand...

Our water lists Ca but not Iron, which I would really like to know since I think it is high. Can a basic carbon filter reduce Iron?

I've been thinking of using half demineralized bottled water and half tap water to reduce the iron and stil have some minerals in it. I, with my hypersensitive to beer flavor mouth has been detecting a slight metalic taste in my beers of late. Also noticed the toilet tank seems to have some iron deposits and the house is only 2.5 years old.

Why can't it be Gold deposits?