Are there better options for connectors/couplings than inserts? I am asking because there is a decent elevation change where the pipe will be laid, and the couplings recommended by big box stores are insert, and will obviously reduce the size of the pipe in a few locations, where I join the pipe. I just don't want to slow down the water too much before it reaches the top. I also don't want to pick a material that won't last a long time underground (I'm only going to be covering it by a foot or two.)
I've found a few other options, but they normally say "not for underground use" or that they are for gas lines. I'm very inexperienced with running lines like this, and I wanted to make sure there wasn't an obvious solution that I hadn't found.