About 25 year's ago the tennis shop at the club i was working at had just installed two clay court's with sub-surface irrigation like that. They thought the clay was too dry so they wanted me to turn up the water. There was a 1" valve for every line under the court. It seem's like there was a line every 8', i really don't remember. The valve's were halfway open, i opened them up 25% more. I came back 2 hour's later and the court's looked like the surface of a lake on a windy day, very wavy. They had to close those thing's for 2 day's and roll the court's for about 4 hour's. I learned something that day.