Poor efficiency

[JabbA]

The last two brews I've done have been quite a bit out on the OG, 3 and 4 points. Generally I hit it with no problems, working on 75% and GWs recipes. Could the fact that I'm coming to the end of a sack of MO be the cause?

I think I'll add an extra couple of hundred grams in for my next brew...

Cheers,
Jamie

[Zatoichi]

Could be, but equally variations in water quality and PH levels during the mash could be the culprit. I buy my malt in 25kg sacks which usually last me 2 months a piece and have never personally suffered this problem. Also are you taking regular temperature readings? (strike and mash)

[JabbA]

Thinking about it, the mash temp could have been a little high on both batches- they both ended up at 66/67'C after 90 mins, I normally lose a couple of degrees. The pH on the first brew was spot on but the second was a little low ~4.9. I'm still playing around with my water treatment (we have very hard water here) and have added a tsp of Gypsum to the mash and the boil. I'll drop it from the mash next time see if that make a diffrence.

Cheers,
Jamie

[Zatoichi]

Im no expert like some of the guys on here but I would definitely keep the gypsum in the mash but discard the addition to the boil. Im in Southampton and the water is very hard here as well, personally I find a teaspoon of gypsum in the mash water and one in with the mash itself works wonders!