How fragile are these t fittings?

 

Just snug it down very, very lightly. Once the O-ring makes contact in the recess stop, and then just barely touch it a bit more. The only thing important is that coolant doesn't leak from the bleeder screw. It is very easy to correct undertightening; more difficult to correct overtightening.

I tightened the one on my truck three times, maybe four in the last week as I first drained the coolant and then flushed the system three times with distilled water until it was almost completely clear before refilling with 2 gallons of Prestone concentrate to bring the dilution to 50-50. Breaking the screw is not something to be concerned about, in my opinion.

What would worry more are the brass screws that so many seem to prefer. The danger with the brass screw is that you tighten it too much and crack the T fitting. Then you are up a creek, buying an entire new upper hose assembly Unless you can snag a T from a boneyard truck..

 

I see you're from Ontario.
All Canadian Tire locations will have a big green metal bin where you can put containers of used oil, coolant, empty spray or paint cans, etc.
They normally ask you do it during working hours because some people just drop their crap on the ground beside it and it ends up with a spill. That's where I have been dropping my used stuff for many years. There are many studies that also show that coolant is not bad for the environment (other than killing cats) but I normally don't take a chance for the first emptying of the coolant, during the rinse with fresh water I don't bother collecting as it's very diluted anyway. Just think of airport de-icing, they collect some but lots just flies off the wings when the plane takes off. Most likely a lot more than what's in your car.

 

Go on youtube and look for Marketplace Economy Lube.
That's one shop who got caught systematically charging for work that was not needed and they did not even do in the end. Cars coming with pink coolant and they just siphoned what was in the expansion tank and refilled with green coolant... It's worth watching.
You will say that was one crook and his business, but maybe there are many others.
Only an independent trustworthy mechanic or myself will do such job!

 

You also want to fill the coolant when the engine is stone cold. You have to follow the procedure in the RAVE when filling with coolant so you get all the air out of the system.

 

In my area, you can dispose, for free, of liquid chemicals such as motor oil and coolant.
You poor the liquid in a translucent container (according to the Waste Management flier), stick a 4" by 6" name and address marked label on it and set it next to the garbage bin, weekly.
I do so a few times per year and never any fuss. Check with your local waste pick up. the limit here is one jug per week so it takes 2 weeks for any one fluid to get out.