We installed a “T” on the main water line with a valve on the down leg of the “T”, this makes it real easy to blow down the car wash. When we close down during freezing weather we turn off the power to the equipment, close the incoming water supply valve, and connect air to the valve on the “T” blow air into the water system to move the water out of the high pressure lines. I suggest you pump -20 degree windshield washer fluid into the water as you are not going to be able to blow all of the water out of the water hoses, to many low spots and valleys in the hoses. Your Foam brush, presoak and any other low pressure system you have you’re going to have to drain your tanks and start the pump and pump -20 degree windshield washer into those systems so they don’t freeze. We’ve got it down so we can shut down the car in freezing weather in less than 10 minutes and have it reopened in less than 5 minutes, it’s all about being prepared. We have everything we need to shut down the car wash staged in a buckets ready to go up in the attic, 5 gallons of -20 degree windshield washer fluid, it's $1.78 at Walmart, a Flojet pump, hoses, fittings that we might need.