leak in main drain?

last year we had to add a lot more water into our in ground pool than previous years.

I did the dye test inside the pool except down by the main drain, which is where the leak is I believe.

• When I close off the main drain at the valve by the pump/filter, there are no bubbles in the pump basket.
• If I put the valve in the middle, so it's 50/50 with skimmer and main drain then there's a few bubbles.
• If I close off the skimmer then the pump basket is loaded with air bubbles.

My neighbor is going to dive down to my main drain and do some dye testing and research the problem down there in the deep end. I'm hoping it's something simple and not too expensive to fix. At the end of last season a company was going to come out to leak test things for $350.00 the first hour and then see how long it takes for results. I didn't have them come out because he couldn't answer me how he was going to leak test the main drain without going in the pool and plugging it?

Anyone have any thoughts or comments on this?

thanks Randy

Finding leaks is difficult and uncertain at pool side; doing it via the internet is . . . almost certain to fail.

I'm sorry, but I have never come close to finding a way to help much with leaks via the Forum.

HOWEVER, the valve process you describe suggests that you have a broken main drain line OUTSIDE the pool, below water level (since it leaks), but not very far below (since sucks air). Some leak testing companies can close the MD line at both ends, pressurize it, and locate the leak -- approximately -- via sound. Then, the digging begins . . .