It is not safe to swim in (unless you dump tons of chemicals in it) or never safe to drink. 

I have many clients that regret going the cheap route in the past to the tune of thousands.What will chemicals run me?

They charged a lot for chemical cleaning of AC and pressure check etc.

I know others have simply taken a garden hose and sprayed the nest, but the sprays have chemicals that will reduce the chance of them rebuilding the nest in the same spot.

The back house was sprayed 6 months ago and the tenants took necessary procautions to prevent future bed bugs ( fully encased beds and use of professional chemicals) but the main house decided not to spray at the same time.

I mentioned farmland, prime farmland with a good water source, land that was not denuded by modern chemical farming, land that was near population centers (who are you going to sell to?)

Even if this chemical/tab/whatever actually does reduce the heat required for a combustion, there is no benefit to that for a diesel engine.

The Home Depot carries flappers that are supposed to be more resistant to the tank chemicals, and just a couple of dollars more.

Robert that is child's play.What you have is a cleaning party and paint.I consider your property left in nice condition compared to some of mine.I will say from your outside A/C unit you could use a chemical clean to the coils for better air flow.I personally treat this like a business.

They begin to get "hooked" - almost like a chemical reaction and pretty soon they are buying properties based on completely different criteria than the ones they first set out.Character - Doesn't need much explanation does it?