I have a Febco sprinkler backflow system (don’t judge me. it was here when I bought the house). Because whoever installed it did not put in drain valves, the ball joints have split probably every year it was installed. I am thinking of cutting out all of the copper pipe and installing new pipe with a valve at the low end of each side of the back flow to properly drain the system for winterizing. I know that ball joints are the weak point of these systems because water gets between the ball and the brass and cracks it when it freezes.
Is there any reason to not use a gate valve to drain the system?
Speaking of that, why wouldn’t I replace the inflow and outflow valve to the pressure vacuum breaker (both are split) with gate valves since they are either open or closed?
Gate or ball valves will work. I have a similar set up. Upstream of the backflow I have a shut off valve (gate, because it’s what was there), and at the bottom of of each backflow riser I have a tee with a hose bib for a valve. When I expect a freeze, I shut off the upstream gate valve and then open both hose bibs, where about 16 or so ounces drain out. Mine is PVC so adding the tees was easy. I used hose bibs because they were cheap and hey, I can attach a hose if I ever need to.
The main reason for preferring a ball valve over a gate valve is that you only need a quarter turn to completely close or completely open a ball valve. Just by looking at the valve handle, you can tell if the valve is fully closed or open.
Also - gate valves don’t age as well as ball valves. They will leak over time.
I don’t know where the OP lives, but here I run the sprinklers year round. Pipes in the ground aren’t going to freeze, but that backflow sitting a couple of feet above ground level? Yeah, it can freeze. With the valves I can protect the backflow without having to drain the entire system.
But gate valves will allow a smoother turnoff of water and resist water hammer which can destroy your fixtures. You should talk to your local bldg dept and ask them or get a licensed plumber.
I just looked up Febco backflow valve and the pictures I saw had appropriate fittings. YMMV. You can get fittings to attach an air compressor to a threaded faucet as well.
This is the guide for winterizing my system. Read step 2 about opening valve E and notice step 3 that says open valve E and close valve D to blow out (which is optional) the system? Valve E was never installed in the piping which means I’m going to have to install one.
Oh and drain B was not installed either. I checked when I turned off the main valve under the house.