Someone posted a link to a youtube video a couple weeks ago, they took doing their Class C MH, which would be very similar to your Class A. I did not watch it, but there was a number of good comments on it. A search could be beneficial.
Being your first time winterizing, I would recommend doing a "dry run" first with a bucket of water before using the RV antifreeze (make sure it is RV antifreeze safe for human consumption). At minimum I would have 2 gallons on hand. For my HTT, I use 1 -1.5 gallons.
Couple things to note, there are a few different approaches to get the task done. Below is a list were people tend to struggle or makes an error.
#1 your MH will use the city water connection to draw the antifreeze into the system. There is a cone hose washer on the city water inlet. You need to flip this cone washer over, allowing the screen to press on it the check valve. Inturn, this allows the pump to draw fluid into the system. Don't forget to flip it over when done, or in the spring your pump will draw air instead of water from the tank (common issue).
#2, Do you have any on board water filters? If so, remove them. It can take a few gallons of antifreeze to flush the water completely out of them. Better to drain/remove it first. Might have a whole house filter, or just for your kitchen sink, might have one for a frig with water. Your rig is designed to have at least one filter. On some rigs they are often very well hidden and a pain to get to.
#3, I think we all have made at least some of these errors at some point.
- Have a tanked water heater? Drain it, then bypass it. It is always fun to fill the water heater with RV antifreeze and scratch the head and inquire where did it go?
- Plumbing low point drains, make sure to close them, see above
- Don't forget the outside shower
- Don't forget the toilet
- Don't forget the shower head. I disconnect the hose, and let it hang and naturally drain.
- Don't forget the washer hookup, even if you do not have a washer, but it is an option, the water line is there, and has water in it.
- Most people do not forget the frig (water/ice dispenser if you have that option). It too has a water filter, and most people seem to shake their head at where to begin to winterize it.
- Waste Tanks, make sure to drain them. I try to do a good drain the last time we are out. At home I always put a 5 gallon bucket under the drain and let them drain. DO NOT dump into your yard, especially into a vegetable garden, Dispose of it down a toilet.
- If you have a Sanicon Macerator, they can hold a few gallons of water behind them. Extra antifreeze will be required, or it needs to be disconnected and drained.
- Black tank flush, should be winterized. Compressed air or flip the cone washer to let it drain)
I think that is were most of us have had our learning curve moments.
It's a fairly simple process. But there are a lot of devices that need to be protected. If this is your first time winterizing doing a dry run first. This will let you walk through the process, and not run to the store 3 times.
There are a few options when winterizing. At minimum it seems like most people start off with opening all the low point drains, faucets and let the water naturally drain from the pipes. This allows you to use less antifreeze, as there is less concerns about it being diluted.
Some people including myself, like to blow compressed air through the system before and after winterizing. This does a nice job pushing the fluids out of the system. If you go this route make sure to have the regulator set to a low pressure. Under 40 psi, I tend to set mine around 30 psi. It does take a lot of air. I go around, open each faucet, low point one at a time, and force the water out of the system. I usually go around to each device a few times. I also open and close the low point drains and water heater bypass when I do this to ensure no water is trapped behind any of the valves.
When happy, verify all the faucets, low point drains are closed and verify the water heater is bypassed. Pump in antifreeze. Pending on your system, the pump may draw about 1/2 - 3/4 gallon of antifreeze before any start coming out of any faucet. If more than that, it could be dumping on the ground (low point drain), or into the water heater
If you did not blow out the lines first, you can tell you have a good concencentration of antifreeze as it tends to be a bit foamy as it goes through the aerators. Do plan on having an extra jug of antifreeze.
Once I have pushed antifreeze through the system. I pause for a moment. Walk through the system make sure I hit every device. I have forgotten the outside shower once. I suspect I forgot the toilet once. Once happy, I disconnect the antifreeze suction hose.
If there is any extra in the jug, I hold on to it for a while.
Optional step, I blow out the lines again. Antifreeze really does not need to be in the lines over the winter. You just need to displace the water. I liked the lines drained because where I use to store my TT, it would get close to -50, so I like having the extra space in the piping for it to expand if I made an error.
Once happy, I take my extra antifreeze, and pour it down the drains to ensure the traps are well protected. Make sure to have plenty in the shower drain.
If you have an Sanicon, determine if you need to pour a few extra gallons of antifreeze down the tanks to protect it. Some people have reported, up to 3 gallons of waste water sits behind it. I believe every time I have heard of such large volume it has been with a 5ver and not a MH.
An alternative to using RV antifreeze is to only use compressed air to blow out the lines. I have not heard of anyone comment they have had any broken pipe issues. They still have to place antifreeze down the drains.
I like the belt and suspenders approach, Compressed air, Antifreeze, compressed air.
A maintenance item to consider doing at this time, but in the spring will work too. The pump has an inlet filter screen (little cup size device). Recommend opening it up and cleaning the screen. I like to clean mine every fall prior to winterizing. This year mine was super full of crude.
Good Luck and congratulations.