This is just for curiosity's sake--I'm not looking to sabotage my pool or anyone else's. I'm just wondering if anything could go in there that would make really really bad things happen to the pool and/or the people in it!

Chemgeek, Jasonlion, and our other very knowledgeable pool folks (especially those who have probably had to clean up a mess or two in their professional careers) will chime in I'm sure. And while I don't know about permanent damage, there has been posts in the past of people having their pool sabotaged with oil. The guy who had it happen had to make a boom to skim it off the surface and shock & shock and change his sand too I think. Makes you want to catch the person who did it and probably beat the stuffin out of 'em.

Yeah, oil was one of the things I was thinking, based on not only the Gulf situation, but also because I'm the kind of person who would decide to jump his bike into the pool after a few beers

Well then you would be adding gasoline & oil & break fluid, possibly antifreeze depending on the bike and maybe battery acid. I ain't swimming in your pool then

No not a MOTORCYCLE, even I'm not that stupid But my bicycle would still have grease and chain oil.

Okay, I can no longer resist...the absolute worst thing that you can put in a pool is...

A 200 pound block of 100% pure metallic elemental sodium.

That would be bad.

I'll bet that Richard could top my suggestion though.

heh...I did a bit of research on the sodium...

http://www.periodictable.com/Stories/011.2/

...not sure exactly where the line is between THAT'D BE AWESOME and MAN DON'T EVEN THINK ABOUT IT...but it's probably well under 200 pounds

In all seriousness though, the things that under normal pool circumstances, I would consider the be the worst for introducing in a pool would be just about any hydrocarbon or a big bunch of fertilizer. Gasoline seems to me to be something that would really be tough to deal with, even more so than straight up oil.

hehehe mythbusters did that in a smaller amount. big boom. but they also did it with something else that provoked more of a reaction then sodium, but i can't remember what it was.

now that you mentioned gasoline, i would agree that probably would be the worst. if memory serves there is a chemical added to gas, MTB(??) maybe that gets in to the groundwater and permanently pollutes it, no way to remove it. guess you'd be draining and refilling plus changing filter medium plus i'd be very concerned about it leaching in to the piping/liner/filter/etc.

A BabyRuth

Crude oil would be bad. So would Plutonium. Or this guy could empty his load in your pool:

Recently at a family event, a toddler left a turd in the pool. As various family members freaked out, evacuating the pool and suggesting we drain it, my FIL casually picked it up with his bare hands and said "No need to worry, it's clean, it never even touched the ground, 2 second rule"

In my experience the worst thing I ever had to deal with was the one time my boss decided to dye our pools green for St Patty's day.

Sure the label said it was 100% safe for plaster pools but what it didn't explain is how it attaches to the grids of a DE filter...and stays there....until the grid sprouts a hole in it.....and then dumps it's St Patty's day green contents...... all back into your pool.

I got good at replacing grids in DE filters that summer. 9 complete grid change outs.

lmao

Here's some scary thoughts:

Broken glass (never allow any glass products anywhere around your pool) Once my daughter dropped a light bulb right by the pool- luckily none of the glass got in it- whew!)

Paint (oil base is worse than water based, but wouldn't want either!)

Regular diaper (as opposed to a swim diaper- yeah, my sister in law put her kid in our pool once with a regular diaper- it immediatly absorbed 20 pounds of water and then chunks of goo went all over)

Poo- (once a neice pood the pool- luckily I just had to remove the turds and shock) (and once my youngest daughter pood her swim diaper in the pool and it was a loose one- the swim diapers catch chunks, but poo water was dripping all over- another major shock event)

A pet peeve of mine is when people come over and put a whole bottle of sunscreen on and then want to immediately jump in the water. I make them wait at least 20-30 minutes to make sure it's absorbed before they get in (a good test is to wet their arm or leg- if it immediately turns white, then it's not ready- if they get in too early, all the sunscreen comes off, clouds the water, creates a terrible scum line, and they sunburn and think it's your fault)

A potted plant- keep them far enough away so that they don't get knocked in or blown in by the wind.

Pool furniture (especially if you have a vinyl liner that could tear or puncture).

Animals (once the outside cat was drinking out of the pool and fell in- it was funny to watch, but could have punctured the liner clawing his way out- luckily somehow he didn't). I also think it's totally gross to let your dog swim in the pool unless he's bathed and brushed frequently. Haven't had any problems with snakes, but we've had a few shrews end up in the skimmer basket- gross!

Trees- when hurricane Gustav blew thru, an oak tree fell right between the house and the pool- MAJOR mess, but we got lucky again and although there were lots of leaves and sticks in the pool, nothing hurt the liner. The sap that dripped all over the pook deck took forever to clean up!

Body jewelry- true story- went out of town on vacation and my brother in law house sitted for us and had a pool party- when we got back, the pool was milky cloudy and we found a body piercing ring on the bottom of the deep side (not sure what part of the body it was from or whose it was!- GROSS)

Intoxicated guests- you know they're gonna pee the pool- watch the CC

Vomit- just gross

Personally, for me, it would be my ex wife

My first thought was a bag of cement. (Not for the ex-wife, but as the worst thing in the pool. Of course, the bag of cement might solve the ex-wife issue also )

Here's a good one...
topsoil-is-good-for-pools-right-now-with-photos-t20586.html

My first thought was that you were on to something, and then I realized not only would she be in the pool, but how would I get her out

Do they make a sequestrant for that?