Best way to add sightglass

There are many ways out there but my keggle has a 1/2 fpt threading. I would like the sight glass to stay close to the keg. and the coupling already sticks out a it. Think a street tee? then how would you go to the smaller compression for the glass tube? Or would it be better to drill and tap something?

If you use the existing fitting for anything else that has wort or water flowing through it, then the sightglass reading will be affected by that flow. Draining out of the fitting will reduce the level of liquid in the sightglass, pumping in through it will raise the level, so you get false readings. Since the point of a sight glass is to be able to track the level of the liquid in the keggle, I would put in a dedicated fitting for it that has no flow except liquid into and out of the sight glass. This way you get acurate readings that you can use to control filling and draining operations. You could use the open end of the Tee (if you use a Tee fitting) for a thermometer or a thermocouple for example. Or you could use an elbow fitting just for a sight glass.

Yes, but wouldn't the flow adjust back out as soon as you close the valve back off? I'm pretty sure it would.

I wanted to be able to measure closer to the bottom of my HLT, so I turned the Tee sideways and used a 90 degree compression fitting to get the site glass vertical. If you have the tee vertical and add a compression fitting to it, it becomes so tall that you can't measure volumes near the bottom.

aj: yes the level corrects when the valve is closed, but trust me, it's a pain. My HLT has a sight glass T-ed into the drain/fill valve, and I get tired of opening and closing the valve to get a true level when I am trying to get a measured amount of water into my MLT. The level bounces around so you have to wait for it to settle down, and if you are dumb and in a hurry like me, then water shoots out of the top of the open sight glass when you are filling it. It's lots easier to have a separate fittings for sight glasses if you can.

Ah, all very good points. I was seriously considering using the same hole for sight glass, thermometer and valve. Now you have me reconsidering. Although, I have no plans to fill using this hole so I at least don't have that problem.

Its a non-flowing joint, just want to be carefull so the sight glass is not too far from the keg or so tall that i can't get a good low reading off it.

more im getting at it seems not many kits are made for 1/2" fittings and brainstorming how to adapt