Fly sparge question

Hi guys, have a question if you could help me out. I made a wheat beer earlier and while fly sparging I hit 1.010 so I stopped the sparge. Unfortunately I was just under 8 litres short of my pre boil volume - although my pre boil gravity was exactly as it should be. I sparged really slowly, timed it at 500ml every 1 minute so I just decided to go and start the boil and just end up with less beer this time.

I left the mash for 15-20 minutes and decided to check the gravity again and it was now 1.025 so plenty of sugar left. How can I stop this happening next time I brew a similar beer? I shouldn't need to stop for 15 minutes then continue fly sparging should I?

Sone said:

Hi guys, have a question if you could help me out. I made a wheat beer earlier and while fly sparging I hit 1.010 so I stopped the sparge. Unfortunately I was just under 8 litres short of my pre boil volume - although my pre boil gravity was exactly as it should be. I sparged really slowly, timed it at 500ml every 1 minute so I just decided to go and start the boil and just end up with less beer this time.

I left the mash for 15-20 minutes and decided to check the gravity again and it was now 1.025 so plenty of sugar left. How can I stop this happening next time I brew a similar beer? I shouldn't need to stop for 15 minutes then continue fly sparging should I?

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It seems like it was just going too fast- 500 ml every minute is fast.

It should take a good 45-60 minutes to fly sparge a 5 gallon (19L) batch.

Really, I'm sure I read 1 quart/min when fly sparging is a good figure to aim for which is why I went a little slower still. It would have taken me 58 minutes to reach my pre boil volume of 29 litres. What speed would you suggest I try next time?

Sone said:

Really, I'm sure I read 1 quart/min when fly sparging is a good figure to aim for which is why I went a little slower still. It would have taken me 58 minutes to reach my pre boil volume of 29 litres. What speed would you suggest I try next time?

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There are a lot of factors- graincrush, manifold design, etc, but you need to go as slow as you need to go in order to get more quality wort.

If it takes an hour for 19 liters, then it would take half again as long to get another 9.5 liters out at that speed.

You may want to consider batch sparging, if your mash tun design isn't well suited to continuous (fly) sparging, or if time is a factor. Batch sparging can be as efficient as continuous sparging, especially with some set ups.

If you are doing a wheat beer, the mash can get a little gummy from the beta glucans in the wheat malt and that can significantly influence the sparge. To get around this issue, I would recommend using a bit of rice hulls to make sure the mash is not sticking together too much. In a five gallon batch, you should not need any more than one pound of the hulls. This will help to loosen up your mash and encourage a more even sparge. In addition to using rice hulls, be sure to keep your sparge nice and slow, dont be afraid to take it to 90 mins. Another trick is to lightly slit the top of the grain bed during your fly sparge with a spoon or similar to encourage even flow of sparge water through the grain bed. Just try not to disturb the bottom few inches of the grain bed that rests on the false bottom.

Great information thanks, that does make sense as it was quite a gummy mash when finished (I've never used wheat before) so I guess I experienced some channeling? I've been reading and with my MT (a square cooler & copper manifold) I should not have the manifold close to the walls as this will also encourage channeling and my manifold is right up against the walls! So I'm going to cut it down about an inch all the way around, sound a good idea?

I will be sure to use rice hulls in the next wheat beer and see how I get on! Thanks again

Sone said:

...I should not have the manifold close to the walls as this will also encourage channeling and my manifold is right up against the walls! So I'm going to cut it down about an inch all the way around, sound a good idea?

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I would definitely agree that is a good idea. By cutting it back a little bit it will be more likely to collect wort that has actually traveled through the grain bed, and not just down the sides of the cooler.

Sone said:

Great information thanks, that does make sense as it was quite a gummy mash when finished (I've never used wheat before) so I guess I experienced some channeling? I've been reading and with my MT (a square cooler & copper manifold) I should not have the manifold close to the walls as this will also encourage channeling and my manifold is right up against the walls! So I'm going to cut it down about an inch all the way around, sound a good idea?

I will be sure to use rice hulls in the next wheat beer and see how I get on! Thanks again

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Using a square cooler and manifold is not well suited to fly sparging. It has to do with the shape of the cooler and the flow. Try batch sparging, if you plan on keeping the design you have. Changing the manifold won't really help, as it has to do with the shape of the cooler as well.

Batch sparging will be more efficient with the design you have, plus save an hour of your time.

The fact that your runoff increased in gravity indicates two possible scenarios. First, you were channeling sparge water past the sweeter wort during the sparge. The pause caused the whole tun to equalize at the average gravity of 1.025 almost like a batch sparge. The second possibility is that you started sparging before the conversion was complete. I'm leaning towards the first one.

I have not seen the answer to this question anywhere, If I am fly sparging for 30 or 60 minutes, how do I keep the temperature up in the grain bed, without adding heat of some kind? Or, does it really matter after the initial mash?

MindenMan said:

I have not seen the answer to this question anywhere, If I am fly sparging for 30 or 60 minutes, how do I keep the temperature up in the grain bed, without adding heat of some kind? Or, does it really matter after the initial mash?

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I sparge with hotter water, so that the grainbed stays at 166-168 or so. I mash out, then sparge with 175 degree water. It drops a couple of degrees from the HLT to the MLT, so the water going into my MLT for the sparge is 173.

Yeah I'd agree with you Bobby_M, I did an iodine test and had full conversion so it must surely have been channeling that caused the issue. I have been reading that fly sparging lends itself much better to circular mash tuns & false bottoms so that is something to keep in mind for later.