SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

I have a 20x30 garden that I want to irrigate. I have several different types of sprinkler heads that are circle and rectangular spray patterns. My problem is that I don't have enough pressure to operate them. I bought a booster pump from harbor freight but it still doesn't have enough pressure. The heads do not even pop up. I have the heads connected in line, 6 total, with 1/2 inch pipe. The supply line is a 3/4 inch garden hose that is hooked to the pump. The pump is rated at 71psi, according to the book, but the outside of the box says that it has a max psi of 36. So I am not sure what it is really. The hoses on the pump are 4 ft each so what ever the psi really is should not have any loss when it enters the 1/2 inch pipe to the heads. What do I need to do to get this to work?

My knowledge of lawn irrigation is next to nothing, so that is why I came to the experts for advice. Just tell me what size pipe that I need to use and as to how many sprinkler heads to I need to cover the area. Thanks for your help, I appreciate it.
Oh and I understand the Harbor Freight opinions, I was looking for a quick fix, I am taking it back tomorrow and going to get a better pump, but I am not sure what I need to buy.

Just wanted to see if I could get some answers, thought that was what forums were for. Sorry to have bothered you, I'll go look for answers elsewhere.