You want to contact BJ's Cap-Drains 352-259-2744 or 352 454-6448 web site
BJ's Water Cap Drains for Screen Rooms He has done countless lanais here in TV. He also advertises on this site. He puts water down in your Lanai to see where the water pools and then installs drains in those areas. I even had decorative concrete on my Lanai and he was able to install them with no problem. The water now drains from my Lanai immediately after it rains.