Belgian Triple - Is a blowoff inevitable?

I'm getting ready to start a Belgian Triple, but am concerned about the primary fermentation stalling out. While doing the shopping, I'll pick up an extra smack-pack of yeast (Wyeast Belgian Abbey), and will do a starter to give the yeast a head start.

I was planning on pitching both packs of yeast on brewing day - but it seems like adding that much yeast to that much malt is guaranteed to cause a big blow off.

Would it be better to hang on to the second yeast pack, and pitch it once the first round of primary fermentation slows down?

If you make a sizable starter (~3/4-1 gallon) with the first yeast there will be no reason for the second yeast. Providing, of course, the first yeast is also a high ABV tolerant yeast.

Blow off is a definite possibility, although you didn't list your equipment, so maybe not. It all depends on if you have enough head space in your primary. I'd be ready for it though!

I use a six-gallon plastic fermenter. With 5 1/2 gallons of wort there's about six inches of expansion space. I use a typical three piece airlock, don't have a blow-off setup.

When I have a vigorous ferment going with a medium-weight brew, I'll get some foam touching the bottom of the lid, but haven't had any problems with actual blow-off (which I did with a five-gallon fermenter, blowing the airlock right off the lid!)

Thanks for the advice. I'll probably stick with a good starter and hold off buying the second pouch of yeast unless neeeded.

Cool the wort to the low end of the yeast's temperature range before pitching. This will slow the initial fermentation.