question on HLT outlet valve

Those of you using 15 gal kegs for HLT and brew pots....since you can't put the outlet valve all the way to the bottom, are you using a diptube to drain the kegs or just draining to the valve level and calibrating the sight glass tube to match that level?
I know I don't need to be using a diptube all the way to the bottom of the brewpot anyway so it is not as big an issue as getting the amount of water going into the MLT and getting the right amount of wort into the fermenter.
Thanks for any advice on this, I have almost got my equipment right for my switch to AG.
ron

i use a dip tube in mine.

diptube and sightglass

If this is about sight glass levels, read on:

You can have bottom drains. But regardless, you calibrate you sight glass in a brewday scenario. First you put everything in your pot that will be in there on brew day, such as false bottoms, hopstoppers, dip tubes, etc etc. If you pour a gallon of water in and it's not shown on your sight glass, you pour another and another until you get your first marker on your sight glass. If it took you three gallons to get your first level indicated on the sight glass then your sight glass will start at 3. There's a reason BobbyM starts his decals off at the number 2. A sight glass that can indicate one gallon is extremely rare because of the diameter of the bulk head and the 90* fitting height.

So typically once your HLT gets below 2 gallons it becomes very difficult to accurately measure how much water volume you're draining. That's why most people put more water in their HLT than they know they will require. Most people refill their HLT after mash so they know they'll have more than enough for sparge and to get the BK to their boil volume.

Hope this helps and I hope I'm not too drunk to know what I'm talking about.

Thanks guys for the replies.
13asturd, that is the issue I am asking about. On the HLT I have a 90*ell on the inside of my drain without a diptube which still leaves about 1 gallon after draining. My keg already had 2 holes in it when I bought it, side by side and not level with each other, so my options are limited. I used the lower hole for the drain and the higher hole beside it (3/4 in higher) as the lower point for the sight glass tube. When water just shows in the glass, I have right at 2 gallons in the keg but only 1 gallon of retrievable water due to the way I had to set it up.
I am going to make a level indicator that shows 1 gallon at the start of the glass and go from there. Later on I will go with a diptube and a pump and be more accurate tho I am only making 6 gallon batches now.
Long story short, the addition of a diptube is the only change I can make to make it better due to previous owner drilling holes where he did.
Thanks:
ron