Why would a small "bead" of mercury appear in the bowl of my toilet?

Mercury may have been used in Electrical float valves, but never in toilet float valves.

That makes sense. I couldn’t think of how it would be used in toilet float valves, which is why I looked so hard for design that contained one. It would have been a really cool solution to the problem.

In any case, the OP should replace the toilet. It’s not that expensive or difficult. If the Mercury comes back, then you’ve got a problem.

Although I doubt it, perhaps the toilet was equipped with one of these at some point:

http://www.ikecoalition.org/Mercury/hg_toilet_nightlight.htm

(Some guy came up with the bright idea of making a nightlight that came on when the toilet lid was up. Unfortunately, he ran afoul of EPA rules by using a mercury switch in the thing.)

This simplest explanation has already been stated. Somebody previously disposed of a small amount of mercury in an improper manner. If you poke around, such reports are not unheard of. It’s a good point that the dense bead of mercury may just roll out of sight when you flush, only to reappear eventually. In which case, maybe you’ve solved the problem by fishing it out.

So, The Composer, you don’t have a septic tank either?

I do have a septic tank. Two, in fact: one tank for the main floor and the second floor and another tank for the basement. Not sure why they did that, other than capacity. Our plat shows two tanks and I know there have been no repairs or replacements according to the health department.

If you have a septic tank, you should change your toilet yesterday. A small amount of mercury might not be a big problem, but if this has been going on for months who knows how much mercury has gotten into your leach field. Your leach field could be a superfund site.

Float control switches containing mercury can be found in some septic tanks, pumps and sump pumps.

I have two leading theories.

First, someone dumped mercury into the toilet. It tends to settle at the bottom of pipes, and it is hard to remove. The agitation from the toilet and other hydraulic action is freeing up a tiny bit at a time. Dentists have pipes that have mercury settled on the bottom, in traps and various low points. If mercury was dumped, it didn’t go shooting out the house plumbing all at once. It migrates slowly, get disturbed, etc, but isn’t just flushed straight on out.

The other theory is that you have a tiny leak in a float somewhere. I don’t know enough about your septic setup, but you have two tanks. It is possible one of the floats (or both) is leaking and mercury is being siphoned back towards the home plumbing. Not entirely out of the question. ** You might have a sump pump with a mercury leak**. The sump water, if pumped into the house plumbing (not bright, but it has been done), might contain tiny am’ts of mercury from a float leak, and it could be too close to the toilet in question. Plus, a sump pump can pump an awful lot of water, possibly causing some to go back towards a fixture if the drain pipe is overwhelmed. Send in hundreds of gallons of sump water from a sump wherein the pump float has a leak, and it goes into a drain pipe that isn’t designed for that, and some water goes left/right towards the house fixtures and some goes left/right towards the street.

There aren’t a whole bunch of other sources of mercury in the home: Silent wall switches, thermostats, thermometers, fluorescent bulbs, and maybe a couple of other ones that contain no more than a bulb would.

Water doesn’t run uphill, so the basement is presumable lower than the field servicing the main two floors’ septic tank. The basement might have been finished later and they choose to install a second tank instead of a pump up to the original tank. Or the main tank’s field might not have been large enough to accept the volume of the additional basement bathrooms and thus a second tank and field would have been necessary. There might be an alarm float in one or both of the tanks and…

…or, what Philster just said.

Hmm. We don’t have a sump pump, so, my guess is that a previous owner “disposed” of the Mercury from a broken thermometer by attempting to flush it down the toilet. I’ve put in a call to a health inspector from the health department, so I’ll keep you posted on what they find out.

Hopefully it’s not something that will require a lot of cleanup and/or septic system repair. That’s quite scary even to think about right now. However, it’s probably time for the tanks to be pumped, but that still won’t tell me where the Mercury originates.

You also mention that there is an upstairs.

What’s above the toilet?
Do you keep the lid down?

Any chance someone broke a thermometer (or some other mercury-filled piece of equipment) upstairs at some point in the past, and the mercury has only now migrated through the intervening floor/ceiling to be dripping down into your toilet bowl?

There is a bathroom above this bathroom, so I guess it’s possible something could have been dumped there and it has settled. I haven’t checked the tank for that toilet, but I haven’t noticed anything in its bowl.

I wouldn’t expect anything in the bowl upstairs.

Most likely someone dropped a thermometer on the floor of the room above and the mercury skittered into cracks in the floor, under the molding, etc, and settled into the subfloor.

Inspect the ceiling above the toilet where you are finding the mercury and look for any new cracks, pinholes, or discolorations…

Does the pressure regulator for heating gas contain mercury? Can’t imagine how it would have gotten into the toilet though.

NVM

Could this be a miraculous event? The God Mercury (or Hermes, his counterpart) could be showing himself to you. I believe there is precedence in the christian religion where a goddess named “Mary” will show herself.

Mercury is messenger of the gods and a god of trade, particularly of the grain trade. Hermes protects and takes care of all the travelers, miscreants, harlots, old crones and thieves that pray to him or cross his path. He is athletic and is always looking out for runners, or any athletes with injuries who need his help.

Does this help? Maybe you should kneel down before your toilet and pray on this.

At age 8, I certainly would have been the culprit! I might never have found out about mercury thermometers myself. But neighbor kids might have. Bored groups of kids playing with mercury at some point, then dumping it in the toilet after hearing that adults freak out about it.

Did the composer ever find the source of the Mercury?