For a deck that size in south ontario I would put posts in 42"- 48" deep sonotube. Deckblocks can be okayish for tiny decks but you will have problems with a 12x24 on them.

Glad to help. I have some I play with for feed spray cycles growing lettuce and peppers, they are a common thing in the greenhouse world. Good luck with your project!

You can buy "cycle timer" boards for only a few bucks on amazon, or a nicely packaged one that plugs into an outlet for about 25$. You can set interval and cycle from seconds to hours as needed.

The usual procedure is to do the plumbing correctly, then drywall nicely over it and paint. This will look much better for somewhere between hours and many years. Yes, someday you may have to cut it out but overall its likely cheaper and probably less work than a proper access door install.

If one of your boxes has a decent power supply you could pull twelve volts for the fans from that. Plug into your harness and out the back of a case. I cooled a small network cupboard with extra fans like this for years without problems.

For myself a deck on someone elses cement work? A piece of cake and a fun weekend project. On the other hand I have a brother in law that couldnt nail two pieces of wood together to save his life. You likely fall somewhere between. Have fun, take your time and do good work. It will probably take longer than you expect but it isnt a race.

Yes, that. If access is easy, and its not ancient iron or rotted copper, no problem. In other cases, bigger problem. In any case its always possible, just not always easy or cheap. You can certainly do it or pay someone to do it if you want to bad enough.

Unless you are redoing the plumbing, the toilet flange may not be oriented correctly for your vision and could require changing.

I would probably make a one piece shelf with notches in the corners, then use four brackets made of pieces of angle iron the same width as the legs. A single 1/4 inch bolt drilled through each leg and each corner of the shelf would likely be plenty strong. If you need adjustment, drill multiple holes through the legs. (Though shelves have a way of being adjusted once then left forever at the original height)

Refrigerant? Isnt this a water heater?

There could be with a junky heater near flamables. I use a decent metal frame "milk house heater" and keep it away from flamables. They are intended to heat living space. Most fires with electric heaters are caused by poor extension cords and proximity to flamables. Be safe and use a safe heater and it will be fine. Good quality, no extension cord, its own separate electric circuit.

My well insulated slightly smaller (10x12 10ft ceiling) uses one 1000 watt electric heater to keep it toasty warm. In the summer I have one cheap 5000 wall shaker built in. This is in Ontario. Why go crazy, my whole climate control system for a really nice little building cost under 250$. Other than electric cost, why cant you leave it on 24/7?

Most jet pumps will run fine at 60 psi when in good shape. Be sure you are incorporating the lift from the surface of the lake to the top of your house into your math. Also the pressure switch should be plumbed right at the pump. A larger tank allows more flow before the pump comes in, and will lower the number of cycles your pump needs to run but has no effect on the pumps ability to do the work. If you need more lift and higher pressure a submersible pump right in the lake is a great upgrade and does not require priming if you ever run the pump dry.

As the other poster said, use a roll pin. I would use blue loctite anyway, tighten your thread, then drill for a small roll pin. Will last forever, but could be taken apart with a punch and a bit of grunt if you had to.

If the fridge is actually beside in your layout, I would do just that. I would extend your cold line a bit and you could squeeze an inline 1/2 inch quarter turn valve with the correct fitting for your supply line in the box.

Dont use one of those heinous saddle pierce things on your line in a wall, that will be a likely problem down the road.

Edit...yes this probably wont meet some code somewhere.

Find leak, fix, rip up and fix mold and rot. If you are short on funds, maybe a piece of cheap vinyl floor for the short term. you can often get deals on ends of rolls and odd pieces.

I wont speak of code, because I dont know your specifics. That said, I have a similiar situation in a seasonal shack in the north ontario woods. We ran our 10/3 wire about 250 feet inside cheap 1" plastic pipe temporarily about 25 years ago, and its still fine. Gives it an extra layer of protection from treefalls and animal chews. Definitely not code compliant, but safer and neater than many hillbilly hookups I see up there.