You need "water meter couplings" do a search on google and you will see what they look like.
See one of my comments above - they cost about $18 for a pair of them. I when too a plumbing supply place (the big box stores aren't going to have them). You should be able to find them on eBay.
Polling every 30 seconds is not going to work you will miss pulses - could use an interrupt to catch the pulses.