Minimum Length Between 3/4" Copper Fittings

I am putting together some piping in a very tight space. Need to do a 180. Was going to use two 3/4" 90 degree elbows. Is there a minimum gap that I need between the two fitting ends?

Just enough to feed the solder to each side, but why aren't you using a street 90 for at least one of the elbows?

Not familiar with street 90. I am reworking a water meter installation. The plumber made the 180 with the two 90degree elbows, but has too long a pipe between the fittings so everything is misaligned.

A street elbow has a male fitting on one end, so you can fit it directly into the other fitting without requiring any pipe in between.

You'll find street elbows right along side the standard elbows at the supply houses. If you are not familiar with them, you can easily mistake them for standard elbows until you look at them. One point I would make about this project besides the street elbows is soldering directly into a ball valve. Be certain the valve is open when you solder and don't use more heat and solder than necessary. Too much of either can damage the valve. Pros may have some more advice on this.