Yield and other questions

Due to space and other restrictions I'm using a fruit juicer to get my juice.

At the WE I got around 18L from 30kg apples. The pulp was still damp so I'm wondering what kind of yield I could get from a press?

Secondly, I have 2x9L in 2x10L demijohns. The book I have suggests topping juice up with water - is this a good idea?

Also, my first batch tasted quite nice, but the night I had a few pints of it, I also had a case of the trots! What happened there?

Cheers in advance!

How much homebrew have you had before? Could possibly be due to excess yeast, it can wreak havoc with your system. Cider is also kinda odd to your system at first, just the sweetness and the potency, I'd try again for research and see what happens!

All of the live yeast in my bottled home brew gives one of my room mates really bad gas ha ha, it's normal.

Seriously, my stomach ballooned up and I had 5 very unpleseant trips to the loo, the experience was akin to food poisening.

Were you eating Taco Bell with your cider?

You can add water to your cider, but don't add too much. The more you add the more you dilute the flavor. You will also reduce the gravity and will have to add sugar to make up for it. If you're just topping off the airspace at the top of your botle, don't worry about sugar.

If you drink your cider still like a wine then you might want to consider using a filter to remove the majority of the yeast form your cider before consuming it.