No challenges due to freezing here in zone 9, but let me speculate on your questions. It is unlikely air will freeze if it is moving or even if it isn't moving. However, assuming you are talking about a PVC ball valve, it is a mechanical device that might freeze up and even potentially fail. 90 degree elbows are a big issue with water flow, but much less of a factor in airflow.... unless you have numerous elbows, then you may encounter some minor problems. In general, the more connections you have the more potenital for leaks. Speaking for myself, I only have one 90 degree elbow in my air diffuser system and none in my water flow system (5000 gal koi pond). So, if I were you, I'd avoid putting any ball valve (water or air) in a location were it could potentially freeze and fail. Just my two cents worth... good luck on your project.

I've been booking online for years - that the only way I do it anymore. I use cheaptickets.com. None of them charge you anything, just like a travel agent would not. There aren't any risks as far as I'm concerned. Just use one of the major travel sites like Travelocity, Expedia, etc. Any way you book a flight is going to go through an online computer system, whether it's through a ticket desk at the airport, by phone to the airline, with an agent, or through an online service. In all of the cases, I would call the airline directly to confirm your reservation a day or so later. You can find out about seat assigning at that time.

The Southwest website has a very cute "chalkboard" tutorial that explains how the seating and cattle call works. We checked in online about 16-20 hours in advance, and got number 50 in the A group. When we flew in May, they boarded group A, then families with children, then B and C. We were at the very end of group A (60 per group), and there were plenty of seats left when we got on. We found it easier than other airlines where we ended up standing in line to board even longer than we stood in our group. Plus, the price makes it so worth it.

I consider this forum to be a community - at least that was how it started out. It is certainly not meant to be as narrowly defined as TripAdvisor, which is larger and varied enough to have many specific subforums. Gardenweb also has a travel forum, but it has very few posts, and so it is rather pointless to expect to get much information there. We used to have a dedicated "conversations" section in this forum, but it did not survive the transition from Gardenweb to Houzz, even though many people still wanted it. Since we no longer have that section and many of us still feel like a community, we occasionally have O/T threads - none of which are meant to offend. As for Alitatlia, I will say that I had a very good experience with that airline, but that was two years ago, and I would think that you would prefer to read more recent reviews, since the airline has experienced labor problems lately. I hope it survives, one way or another, as I intend to go back to Italy in the fairly near future, and it had the only non-stop flights from LAX to Rome. I posted the question on this forum because I am familiar with many people who regularly post here, I value their opinions, and I know that many have been to Italy in the past. If I post on TripAdvisor, I have to rely on the kindness of strangers, but I have gotten good advice there as well, especially for Fiji, and I learned about the Fiji forums on TripAdvisor on this forum. By the way, I did a Google search for Alitalia and did not find this thread or forum at all, and so I'm not sure how you found this!