If you are referring to the LPP (low pressure pipe) systems I had one of those systems in a house about 15 years ago and have sold several hundred homes with that type of system in it. They aren't that complicated and for the most part work OK. I have saw the most problems when installed on a steep lot with rocky terrain. You usually have several branch lines of 1 and 1/2 " pvc pipe with a ball valve on one end and a clean-out on the other and you need access to these with a small round pvc box that sets above or even with the ground. They boxes are a PIA to mow around so try to get the installer to make the tops of the access box flush with the grass so you can drive over them,

Thanks LOTO, I think the low pressure has something to do with a gravity system. This whole thing is a mystery to us. Would love other thoughts..

Can't a mound system be used? Would think that would be cheaper and less complicated. Of course, there would be a mound in your yard.