Broken line under pool deck

[JRFred]

I lost about 6 to 8 inches of water in a couple of days, found sand accumulation by one of the steps and sit-outs. Also found moisture on pool deck out of expansion joints --Everything on the same side--I think I have narrowed it down to the line that feeds from the booster pump to the outlet where the pool cleaner hooks up--because it only does it when the cleaner is running. Everything appears normal if I only run the filter (main) pump.
Question: What's the best way to fix this? Set up the cleaner with a new line or go under the deck and make the repair?

[czechmate]

You will pretty much have to use the same input piping due to the quality of the original pipe seal in the gunite.
Going under the deck is expensive and cumbersome.
Consider direct excavating and replacing the section of deck with smartly design cover-up like a section of flagstones etc., even matching one more spot on the perimeter.
It all depends on the level of investment. You need a good reliable access to the repair spot.
You can postpone this till spring, by plugging the inlet with a threaded plug as well as the output on the booster pump. Make sure you disconnect the load side of the time clock for the booster !