My fresh water system is so called “winterized” after each camping trip. Something we have not really talked about on the forum here yet is drinking fresh water systems but that is truly another post.
I know I “might” be on the other end of the spectrum with this mod, but when I upgraded my pump to a variable speed pump I also changed the location to be easy access and a compressed air blow out feature. It is also setup for air blow out in all directions.
The latest version with the shelf over the top on the T310SR.
The prior version with explanation.
And here is the T2499.
From the 2 Sunlines I have owned while I do use the low point drains as part of an air blow out, I have found they to do not gravity drain out all the water to my satisfaction without the air assist. A least an additional 1/2 gallon of water will still come out of the plumbing. So heads up that your low points drains do help drastically but may not take it totally empty.
The Attwood HW heater always retains 1 quart of water inside when the plug is pulled unless compressed air is used to blow it out. And even then there may be 2 oz left. I came up with the 1 quart direct from Attwood. It is the way the tank is made.
This past weekend I finished up the T310 enclosed tank insulation project and we will try the “extended season” enclosed tank feature the weekend of Thanksgiving when we go camping. Since we winter camp and if the conditions are right, I now can bring water along in the system. The system is still usable with the air blow method however after the camp trip and blow out, I do put the pink stuff in all traps and drain the black and gray holding tanks dry after.
When using the air blow method, it takes a sequence of building pressure, I use 40 psi, purging, building pressure purging to get all the water to stop misting/coming out. I have it down to about 10 pushing 15 minutes on the T310.
If the camper is going to sit and not be used, then I do pump in the pink stuff thru the fresh water system like the T2499 sleeping in the shed.
While I do use the air blow method, regular fresh water chlorine shock treatment to sanitize is still part of my active fresh water system.
Hope this helps
PS If you are using the compressed air blow out method here are some of the unusal places to remember. Many of these have allready been stated.
The outside shower
The shower stall sprayer
The Sealand toilet sprayer.
The black and gray tank sprayers.
The air vent line in the fresh tank fill compartment. This is model specifc if it creates a level holding spot for water.
The pump suction line
The actual water pump pending how your blow out is done.