My beer is always fizzy in the test tube at the end of primary. Its just disolved Co2 produced by the yeast that hasnt come out of solution yet.
HEre is what i would do.
1. take everything.... EVERYTHING you use to brew with and put it in your firmenter. Racking tubes, spoons, airlocks, o rings, grommets, you name it. Remove the tap and bung the hole with one of the screw in plugs. make sure there is no build up where the tap screws in. Fill said firmenter with water and add 1/4 cup of un scented bleach. Fill to the top. Screw the lid on so the bleach solution floods into the top of the lid. soak for 48 hrs.
2. get your self some iodophur.
http://www.esbeer.com.au/category41_1.htm USe this to give the firmenter and everything else a quick steralise before you use it. IT only needs a cap full in 10 liters of water for 10 minuites or so and it can be re-used while it has its yellow colour. just drain use, no need to rinse. lots of places sell it so get it from where ever is easiest. BE carefull of it in didgy little home brew shops though cause some water it down and charge the earth for it.
3. buy your self an old $50 fridge to firment in. put a $40 0-40 deg thermostat in it and brew at what ever temp you want all year round. What you have tipped out would have bought that fridge by now so dont be a tight arse

2.5 cartons of beer for the $20 if costs for a k+K....... VB cartons are almost $40 now so thats a saving of $80/ batch. On the second barch you have your money back and a firmentation fridge to make better beer in. Makes sense when you look at it like that hey.
3. ditch the kit yeast and use US-05 for a dry beer, SO-4 for a sweeter beer, or a good lager yeast
4. Firment at the low end of the yeasts temp range. If its 17 to 24 deg, brew at 18.
5. Ditch you LHBS and go see Mark @ MArks Home Brew in newcastle. He will set you strait with good advice.
I wouldnt go worring about the water too much...... Is it drinkable, if its not an odd colour or bad smelling id day its fine. Sounds like a combo of infection and too high temps to me.
The first kit i did i followed the instructions and held it at 24 deg. Tasted like fruit punch cordial. So i got some SO-4 (best dry ale yeast out at the time) and firmented it at 19 deg. Well it made the beer taste like beer.... never looked back.
hope this helps.
cheers