(3rd) Brew Night Advice

[Carpking]

Hi forum.
Brewing Nut Brown Ale tonight. My third AG attempt. I'm getting the hang of everything but just have a couple of questions.
I dont have any water treatments so when i heat my mash and sparge water is it advisable to use a campden tab in there?
I dont have an immersion chiller yet and use frozen PET bottles to bring my temp down as quickly as possible. Also i can stand my primary outside or in a cold bath. My question is, should this be with the lid and an airlock on as it takes longer that desired to cool, to keep the nasties out (and there will be a lot of bats and ghosts around this evening ). This will keep the heat in but the bacteria out i guess so.... ???
I will be able to drink some of my last brew (chocolate stout) while i make my new one

Thanks in advance for your tips.

[Madbrewer]

Cold bath works well - I used this method for my first two years of all grain, but i would have the lid on the FV except when you are stirring (if you stir occasionally it should cool down quicker). Use half a camden tablet, beer wants to be brewed - so even if your mash PH is off, you should still get a very drinkable beer! TBH I don't do alot to my water other than camden and a spoonful of CRS.

[Carpking]

Thanks MB. What is CRS?

[Madbrewer]

Some food-friendly/based acid? Which is used to rid the tap water of carbonates (lower the PH) .... it's a couple of quid a bottle and will probably last me two years....