When water leaks out the side of the bag it means you're watering too fast. I bet if you pulled apart the media you'll find dry spots after you water.
Don't worry about overwatering at any one time. Obviously you don't want to flood the pot but it's the frequency of waterings that will bring on overwatering issues. Cannabis likes a moist to wettish soil. Too much water too frequently and you don't allow the roots to be able to do the O² exchanges it needs during the dryback period. Essentially you'll drown the roots.
Try not to water in measured amounts. As your plant grows its water needs will change. When I hand water I'll usually water in around a 1/4 liter of water slowly to counteract the hydrophobic conditions the media is probably in, due to the dryback period. I'll let it soak in for a few minutes then slowly water around the perimeter of the pot so that the outer half of the media gets wet until I start to see it run out the bottom of the bag making sure water isn't coming out the sides. If it does I'll stop watering and wait for it to soak into the media then continue watering. I'll then water around the stem and on top of the root ball and, again, wait to see it start running out the bottom of the bag. Once this is done the media should be wet all the way through.
If you want to make it easy on yourself, you can do what I did and use Matrix plates and pads from
FloraFlex. These will ensure that all the media gets wet from edge to edge. If you order them make sure you ordered the correct size for the pot you are using. You can either hand water into them or, when you have multiple plants to feed, you can put them on an automated watering system like I did and not have to worry about missing a water day.
The
FloraFlex® Matrix System is a patent pending first of its kind Top Feeding Wicking System that provides the most even way to deliver water and nutrients to your potted plants. The Round Matrix System can be used with pots ranging from 7.5"-18" Diameters. The Matrix was not designed to be...
floraflex.com
The
FloraFlex® Matrix Pad is part of the Matrix System, a patent pending first of its kind Top Feeding Wicking System that provides the most even way to deliver water and nutrients to your plants. The Round Matrix System can be used with pots ranging from 7.5"-18" Diameters. You will need a...
floraflex.com