Airlock Trouble

Hello all. I have a gallon of cider in primary right now. I'm using an s-shaped bubbler airlock with starsan mixture in it.

When I put the airlock + stopper into the top of the jug, the liquid in the airlock moves almost all the way to the open side of the airlock. Now that it's bubbling, I have cider making its way up into the airlock and bubbles coming out of the top of the airlock. Is there a trick to one of these airlocks to stop this from happening?

Thanks. Also, my stopper doesn't seem to want to push down into the jar far enough to create a nice tight seal. It will sit on top just fine, though. Any problems with this?

place your stopper in the carboy then fill with starsan, this will reduce the pressure in the airlock.

As for the cider bubbling up into your airlock, sounds like a vigouous fermentation, so the only thing you can do is to leave it alone or replace the airlock with a blow off tube.

In the future, leave a little more head space (open air) at the top of the fermentor. In the case of beer, frequently you leave atleast 20% space so 5 gallons in 6 gallon fermentor.
For cider (and wines) I don't know what the recomended headspace is, but it sounds like you could use some.

Absolutely. If you need a quick solution, go and grab a blowoff tube from your lhbs

A good thread, check out the pics of a blow off tube

https://www.homebrewtalk.com/f51/blow-off-tube-help-195148/

I took the airlock off, wiped the rim of the jug and the edge of the stopper with a clean paper towel, dumped the airlock liquid out, replaced the stopper, stuck the airlock into the stopper (empty), and poured the star san mixture into the airlock. This time, when I put the liquid in, it only went up to the max mark on the airlock on the side that is open to the air. I think there must be too much pressure on the cider side due to the lack of head space. Next time I will definitely drink a little bit of the cider before I pitch the yeast (or make a 5 gallon batch in a 6 gallon carboy).

If it's a pressure issue from gases released by fermentation, you'll probably be fine just letting it out every now and then! Don't worry too much about infection, your cider has already had plenty of exposure to the air, and this little isn't likely to affect it.