what are the benefits of a sight glass?

[trx680]

I see some pots have internal volume markings as well as a sight glass with volume markings.

So what is the real benefit of a sight glass?

 

[madscientist451]

Its just another thing to clean, I don't want one.

 

[smyth]

The benefit is that while it's easy to use the markings inside of the pot when you've got water in there it becomes more of a decent approximation once you have an opaque liquid, never mind adding things like a mesh bag, hop debris, and things like that so a site glass makes it easy to get an accurate reading on how much is actually in the pot, however i agree with madscientist451 in that it is one more thing to clean making it generally more hassle than it's worth in most cases.
One case that would make total sense is if you have a "brewing sculpture" or a set up that raises one or more of your pots high enough, or i guess if you just have such a massive pot that it makes it either impossible or impractical to look into the pot. In that case a site glass is one of very few solutions to check the level.

 

[brandonlovesbeer]

The only benefit is if you have a large system. When I worked at a brewery we would use them to watch for the tank to drop out so it would not damage the bottling line by sucking air. And to make sure we did not fill the kegs with a tone of trub.

 

[eric19312]

A sight glass is no big deal to clean--clean enough for hot side anyway. Don't think I'd want one in a fermentor.
A sight glass is easier and more accurate to read than a calibrated stick.
A sight glass is easy to read during a rolling boil in a kettle. Not sure this is the case for etched kettle marks.

I have a 2 tier system and have sight glasses on my HLT and BK. Both are integral parts of my brewing process that I would sorely miss if not there. I used the DIY weldless kit from Bobby M (https://www.brewhardware.com/product_p/lp.htm) and have been very pleased with over 100 batches brewed with these sight glasses and no leaks, cracks or other defects. I can read my 15 gallon brew kettle volume to within 0.1 gallon easily and consistently. I know exactly how much strike water I put in my mash kettle because I measure it from the sight glass on the HLT. I don't sweat sparge water volume when fly sparging, I typically use extra 2 gallons of sparge water and just shut off flow to the BK when the BK reaches pre-boil volume (watching the sight glass during last few minutes).

I am a brew by the numbers guy with focus on recipe repeatability and all aspects of quality control. For me the sight glass vs the calibrated stick would be akin to weighing grain with a bathroom scale. Would it work...sure, I could make that work. Would it be convenient and highly repeatable? Not so much. So in answer to your question...yes there are many advantages of a sight glass. How important these features are to you probably depends on your brewing style. Are you an engineer-type focused on hitting all your numbers, or do you take more of a chef/artist approach?

 

[k1ngl1ves]

It looks scientific and sometimes fancy. That leads to wonder by others, and a higher coolness factor in return.


Admit it. They're cool looking... and useful sometimes.

 

[Cyclman]

For big batches I use a 3-tier. A sight glass is easier and safer to monitor volumes. Not difficult to clean at all. I wouldn't want a hlt or mt without one.

 

[helterscelter]

I find the sight glass on my mash tun to be very handy during fly sparging. You need to get the flow rate into and out of the mash just right. With the slow rate of transfer during the sparge its difficult to tell if the in and out rate is the same. I keep an o-ring on my sight glass so i can see if the level is rising or falling relative to the o-ring. Let's me adjust the flow very nicely. This is especially hard to get right with ball valves.

This would be quite difficult to do with etched markings.

 

[Hwk-I-St8]

I batch sparge with cooler based HLT and MLT. I think being +/- 16 oz on pre-boil volume is close enough for me to be able to repeat a recipe within the standards of the the taste buds of 95% of the population. I think there's as much or more variability in the natural ingredients that we use than that would introduce.

If I had a setup where looking at the volume in the kettle was an issue, I'd put one in, but I run a 3 tier with the floor being my bottom tier, so I can see inside all my vessels with no issue. The only place I'd even remotely consider one is for my MLT, but it's a cooler, so putting one there would be a huge PITA.

I don't ever find myself thinking "wow, I wish I had a sightglass" for any of my equipment. For those that have em/want em/need em, I'm glad it's an option for you.

 

[stz]

Sight glass is essential when working with large systems where at a glance it is about the only practical way to see what is going on in there. On smaller home brew kit you can simply look at things and I'd say they become more cool than practical. We've a flow meter on the HLT and nobody wants to do the math to see how much water is left when you can just look at the sight glass and use your experience to judge things. On the pilot kit you just estimate based on how much water you started with and it is really easy to look inside. The one on the kettle is good for repeatability, we've a scale up near the top so you know that if the last time your gravity was a little high or low at a certain level you can collect a little more or less without having to climb a ladder. We've also elements installed in different positions and you can figure out when to get them on to speed up the brew day. Again, on the pilot kit you just go until you are 'about there' because it is really easy to look into.

 

[Jamming]

only on my HLT, water values are quick.

 

[schatzke]

I have one on my HLT which sits about 5 ft off the ground. Makes it really easy to get the correct amount of water in it since I fill with a hose from below.

 

[MagicMatt]

A sight glass is easier and more accurate to read than a calibrated stick.

I'd have to disagree here. I went back to using my calibrated mash paddle, because the sight glass has shortcomings when dealing with volumes of different temperatures.

For instance, if you used room temp water to calibrate your sight glass, that means it will be off when trying to gauge the level of strike, sparge, or boiling temp liquid. With my mash paddle, I have 4 different calibrated scales (one per side) - one for room temp, one for strike, one for sparge, and one for boiling.

I know for most the difference in volume here would be negligible, but the larger the batches, the more noticeable the difference. On 10 gallon batches the difference between room temp and boiling is about 1.5 inches vertically. That's quite a margin of error.

So provided you calibrate your sight glass to the level you'd want the most precise measurements of, then you're probably fine. Otherwise you'll need a multi-point calibrated solution.

 

[eric19312]

I'd have to disagree here. I went back to using my calibrated mash paddle, because the sight glass has shortcomings when dealing with volumes of different temperatures.

For instance, if you used room temp water to calibrate your sight glass, that means it will be off when trying to gauge the level of strike, sparge, or boiling temp liquid. With my mash paddle, I have 4 different calibrated scales (one per side) - one for room temp, one for strike, one for sparge, and one for boiling.

I know for most the difference in volume here would be negligible, but the larger the batches, the more noticeable the difference. On 10 gallon batches the difference between room temp and boiling is about 1.5 inches vertically. That's quite a margin of error.

So provided you calibrate your sight glass to the level you'd want the most precise measurements of, then you're probably fine. Otherwise you'll need a multi-point calibrated solution.

What shape is your kettle? My 15gal pot is about 1"/gal. 4% expansion (room temp to boiling difference) is less than half an inch on 10 gal. I pretty much treat the expansion factor as part of kettle loss. I work backwards from desired transfer to fermentor, understanding I will lose half a gallon to chill, and 1/2 to 1 gal to trub depending on hop bill. So if I want 11 gal to fermentor brewing an IPA I want to end boil (at 212F) at 12.5 gal. I will collect 14 gallons of sweet wort and boil off 1.5 gal. I don't worry about expansion of the sweet sort as I laughed into my kettle with heat on and it will be near boil at end of lautering. Sight glass tells me when to stop lautering and whether my boil should be harder or softer.

 

[Yooper]

The only sight glass I have is on my HLT, and I wouldn't be without one.

I can pump my strike water to the MLT with just a glance on that sight glance. If I start with 14 gallons in there, and my strike volume is 6.5 gallons, it's super easy to fill my MLT without opening any vessels at all. I can also set my sparge volume in there, and be all set.

I had one on my old MLT, and I didn't like that- it would get an airlock or vacuum during pumping and it was useless. I don't need one on my boil kettle- my calibrated spoon works just fine for that.

 

[Morrey]

I have factory sight glasses on my two Blichmann kettles and a third Bayou Classic kettle I drilled and added a sight glass. In other words, I wouldn't be w/o them. I full volume BIAB as a rule, and find sight glasses important when filling to the proper level. Also easy to read to know when I have hit my post boil volumes and take all readings in general.

To clean, I usually shoot a water nozzle in the upper port to give the glass a rinse, but then maybe every 4th use, I'll take the plugs out and scrub the glass out. Takes a minute or two at the most.

I'd hesitate to buy a kettle w/o a sight glass...but that's just me.