Bryon,
This is where I buy my fancy stuff,
http://www.kingmetals.com/ I can't find anyone local as a supplier so the shipping is kind of a pain. The few places around Nashville that have some stuff, well, they break out the King catalog and mark up the prices.....as should be since they would like to make money too.
I've been stocking up on 1.5"x1/8" sq tube for my porch. I painted it last year and before summer was up it was back to looking bad, not to mention the boring bees that chew holes in it. Got a surprise for them when I get the materials for the porch. I want to cap it with Brazilian redwood, supposed to be harder than concrete, cannot stain it.
Anyhow, the thing that I noticed about the handrail at home depot(which I noticed and inspected) is, well, in my opinion it don't look like it will hold up. I believe it is bolted or screwed together which in the long run would mean trouble. I have a bad addiction, I notice handrail everywhere I go, on tv, movies everything, something that really has captured me.
Estimating the cost, I sit with the client, talk about what they are looking for, show some pictures when I start getting ideas and so on. Take measurements. Then, just sit down in my office(kitchen table) and start drawing out sketches with the measurements until I have a good design. Then add up your measurements, finials, lambs tongues and so on and wala....priced out. Since your the welder no labor cost :-) I've made railing out of 1", 1.250, 1.5. One I did had a 2" newel post at the entrance and went into 1" with a handrail cap, actually I'll post that pic too. When you price out your steel, I get 20' sticks and to save money and have the least amount of drops I sit down with my drawings and figure out how much 1.5" I'll need and then start cutting them in my mind from 1 20' stick to get the max amount I can, or least amount of drops.
Codes- it's best to check with your local codes department but stairs are 34-36" for the handrail around here. On landings it is 42" for the guardrail. I suppose on a pool you'd want it 42" but that's just me thinking because it is more or less a landing. Your balister spacing is 4", no more. Can't have a 4" round ball fit through, so kids don't stick their heads through. I cut off a piece of 1/2" solid sq at 3 15/16" that I use for spacing. Most stuff from king is set up at that measurement. Spacing off the decking is the same, 4". Basically any openings, 4".
Aluminum- I guess that is good other than the price. When it comes to handrail I see no need in the extra expense unless your just dying to spend money. The handrail I did below the client wanted aluminum at first and I told her I was curious as to why? She said her fence in the back yard was aluminum, but it was powder coated black. I told her unless she just had to have it the expense was not worth it. I told her in my minds eye it offered nothing better than steel when it came to handrail. I told her on a truck bed where you would save weight, yes. If you were looking for a raw aluminum look, yes. The client picked the steel.
The last two pics are of a plant hanger I made, first one, handmade leaves from 16 gauge. I'm proud of that thing.
If you have any questions just message me, glad to help out any way I can.