How a Toilet Tank Works | Basic Plumbing

Okay, so today I'm going to try to talk a little bit about how a toilet tank works. A lot of people are completely mystified as to the very simple machinations of the toilet tank. You can save yourself a lot of money trying to tackle some of these very simple repairs yourself, with a few exceptions when you're talking about pressurized toilet tanks or maybe a flushometer tank inside the wall. Leave that to a professional.

Generally speaking, a toilet you would get and assemble in two pieces, with a water control valve, a seal, and something to flush it, they operate on a very simple principle. When you approach a toilet and the tank is filled with water and it's sitting idle, the way that toilet flushes is via gravity. A couple things happen: you press the tank lever, and a seal of some sort, which I'm going to show you in a moment, opens up inside that tank, water rushes from the tank into the bowl, flushes the contents of the bowl, and then the tank fills back up again, endlessly. Okay?

I've got my little sketch here, forgive my drawing skills. This is a toilet, at the face, when you're walking in and looking at it. Here's my tank lever up here, usually on your left on the top left. This is the bowl, with water in it. You'll notice this little stop right there, I put an X. On blueprints, stops and valves are drawn with an X because it cuts the water off. A little warning: a lot of times when these little valves have been living under your toilet for a long time and nobody's touched them for 20 years, the moment you touch them, water will start shooting from the handle. It's always a good idea when tackling a water-piping repair, or repair where you're dealing with water under pressure from the street, know where the shut-off valve is before that. In case this snaps off or something horrible happens, you can run downstairs to your basement and just shut the main off and triage the situation until a professional gets there and takes care of it. But let's not talk about that, let's talk about this valve working just fine.

A couple of issues happen when we have problems with toilets, most commonly running, and you have the toilet tank sweating. That's because you have a warm environment, or comparably warm environment, with cold water rushing through it. What happens is, water comes up from this supply pipe into the toilet and fills this tank. That ball, everyone's seen this ball, OK? It rises up on the water and simultaneously pushes down a washer sitting inside of this valve head. That washer pushes down and shuts off the supply coming in. That's how this works. When you flush the toilet and this seal comes up, I'm going to draw that in there. There are two positions: that's the flapper, the seal sitting in the closed position, holding water in that tank. The up position, it just kind of gets snapped up like so, and lets all that water rush down. Then this ball drops, lifting the washer away, like so. Water rushes in, it fills, and the tank rises once again, and the ball pushes it down and off again.

Let's say a big service call for me is a sweaty toilet tank and a hissing sound. That's because one of two things, or two things, is happening. This washer inside this valvehead has failed, in which case you need to replace this valve. This old-fashioned one here, made out of brass, is inferior, believe it or not, to the plastic jobs out there today. This is called a ballcock, cock being a valve, this being the ball that operates it. These are replaced, generally speaking today, with what we call a fluidmaster. It's a black and grey valve, you may have seen it, they cost about nine dollars at the home centers,and they just quickly swap out.

If this valve, the washer inside this valve has failed, it's going to fail to stop the street pressure water from coming in all the time, so it's just going to overfill. If the tank overfills, what happens? It rises, rises, rises, and eventually goes over this overflow tube right here on the Douglas valve, this assembly is called the Douglas valve. The reason that overflow tube is there is so that if this fails, we don't fill out the tank, onto the floor, endlessly and flood out the whole house. So that's a safety, there.

The other reason that the tank would be sweating is again, there is water constantly moving in that tank, causing condensation, is if this flapper failed. If the seal failed, and there are a variety of seals but I'm just showing you this for the sake of illustrating a point. If this seal has failed, the water is going to continuously run down into the bowl. You'll see it trickling into the bowl, you'll see the little rivulets of water in th

[lucyc]

Thank you!!! Another thing to check for with the flapper is the length of the chain. Not long after I moved into my condo several years ago, I noticed the water running in both toilets. When I looked into the tank, I noticed that the chain had coiled between the flapper and the hold it's supposed to cover. I unhooked the chain and rehooked it on a different link to shorten the length of chain between the lever and the flapper. Worked like a charm!! :)

[Schmitty]

Tremendously helpful. I didn't know the black column was an overflow - hearing that word made everything clearer. Thanks for putting this on.

[ChuckBaggett]

No mention of how the water gets from the tank into th bowl. The flap opens and water goes where? And where does water that enters the overflow tube go?

[bee]

Nice! I actually learned something new! Thanks Howcast! :-)

[alfonsorivera]

What happened to me was that the chain that lifts up the seal snapped and wedged between the seal and the escape that fills the toilet bowl. I just had to replace the chain which was very easy. Sometimes you think you have a serious problem but when you check it out it turns out to be a minor snag.

[MohammadSharif-qent]

I want to say
Great info.for the learners

[TheUniquePlumberman]

Must be a commission sales company. For about $75-$100 in parts I can rebuild the whole tank. It is mandatory to replace the trip lever, flapper, supply line & fillvalve. The tank to bowl kit, flush valve are done as necessary. Angle stop is mandatory if not a 1/4 turn type as well. Also a dye test is mandatory after each rebuild to assure done well.

[ChuckMarceloDube]

If the upright tube is intended for overflow, why is the water fill hose to fill the tank stuck inside that tube?