I batch sparge and pump in water from under my false bottom when I add my first addition of water. ( I use converted Sanke kegs ). I have been getting harsh off flavours lately. I don't scale back my valve when adding my water and I get a lot of foam on top of the grains. Am I extracting tannins in my mash? I have been going over my process and found out I have some bad habits and this may be one of them.

3 Dogs

Can you describe the harsh off flavor? Is it astringent? sour? acidic?
It might be your mash pH.

Very acidic. Not nice. I use 50% RO/well water. I don't check my PH. On my next brew I will turn down the valve on the outside of the pump when I add sparge water. It doesn't taste like an infection, well there are no vinegar or hot alcohol flavours. I am going to get a water report soon also.

3 Dogs

Do you fill it with your grist, then pump in strike water, or are you talking about your sparge water? What temp water are you adding? Does it mix in well as you fill, or do some parts get much more exposure to the water?

This is after the mash is done. I batch sparge. I drain the mash-tun and pump 170F sparge water into the mash tun via the bottom valve. I stir well but carefully. There seems to be a lot of foam at this point when it is filling with sparge water. I will turn the valve down the next time I make beer to see if there is less foam.

Since you're not checking it, and wells can be pretty unpredictable for it anyways, I'd bet it's your pH. If the pH is too high (above 5.5-6.0) you will get a harsh, tannic astringency. Try a batch with built up water from 100% RO or replace your well water with spring water.

Okay. I don't understand the water calculators I have seen on the net. It just confuses me.

3 Dogs

If there is foam, I'd imagine that would be an indication that there is air entering it somewhere. IS there a reason not to just add your sparge water from the top and stir?