Phantom toilet flushing and air in the pipes, oh my? Help edition.
October 28, 2020 6:47 PM   Subscribe

Our upstairs toilet is having a problem with what I think is phantom flushing. My google research tells me the part that is going up and down is the float cup. Every few days we get a *terrible* sound that makes a pipe rumble and sounds like air to my untrained ear. Do you know what is happening and what we should do?

We are not bathroom saavy but our guess is that maybe water is sneaking out through the seal in the upstairs toilet, hence the constantly filling tank?

In our downstairs bathroom (directly under it) we can hear water like a "shhhhhhh" every so often. And it seems as though every 3-4 days we have an episode where I can feel vibration under my feet in the first floor bathroom from the pipe and it sounds like air movement. It resolves within 20-30 seconds. We have floor drains in the basement with no issue so it doesn't seem like a sewer line issue, but something related to the toilet. Is this what google tells me is an "airlock?"

Is this something that you handy folks out there understand and that we can fix - or do we need to can a professional?

Thank you from someone who wishes youtube videos were enough to identify the problem!
posted by anya32 to Home & Garden (6 answers total)
Check the flapper, the hinged rubber float plug thing at the bottom as well as the float. At my mom's house there was what I thought was a water hammer making a bunch of knocking sounds every couple of minutes, which turned out to be a sticky float slowly causing periodic refilling with air bubbles. Another time at my apartment there was near-constant running of the filler, which turned out to be a warped flapper caused by having used chlorine-based toilet bowl cleaner things in the tank. Chlorine and rubber are not friends!

Replacing both is cheap.
posted by rhizome at 6:57 PM on October 28, 2020 [1 favorite]

Anytime I need to replace a plastic part in a toilet I buy the kit and replace them all. Once one goes the rest aren't far behind.
posted by COD at 7:39 PM on October 28, 2020 [2 favorites]

@rhizome that sounds exactly spot on. And thank you @COD for the tip. I will do that this weekend and hopefully this will resolve! I appreciate your advice.
posted by anya32 at 7:41 PM on October 28, 2020

This sounds to me like water hammer:
At home, a water hammer may occur when a dishwasher, washing machine or toilet shuts off water flow. The result may be heard as a loud bang, repetitive banging (as the shock wave travels back and forth in the plumbing system), or as some shuddering.

On the other hand, when an upstream valve in a pipe closes, water downstream of the valve attempts to continue flowing creating a vacuum that may cause the pipe to collapse or implode. This problem can be particularly acute if the pipe is on a downhill slope. To prevent this, air and vacuum relief valves or air vents are installed just downstream of the valve to allow air to enter the line to prevent this vacuum from occurring.

Other causes of water hammer are pump failure and check valve slam (due to sudden deceleration, a check valve may slam shut rapidly, depending on the dynamic characteristic of the check valve and the mass of the water between a check valve and tank). To alleviate this situation, it is recommended to install non-slam check valves as they do not rely on gravity or fluid flow for their closure. For vertical pipes, other suggestions include installing new piping that can be designed to include air chambers to alleviate the possible shockwave of water due to excess water flow.[25]

Water hammer can also occur when filling an empty pipe that has a restriction such as a partially open valve or an orifice that allows air to pass easily as the pipe rapidly fills, but once full the water suddenly encounters the restriction and the pressure spikes.
In your situation I'd guess it's from the fill valve in the tank in the upstairs toilet. When enough water leaks through the poorly sealing flapper, the fill valve opens up a little because of the lowered level in the tank, water rushes into the tank through the fill valve, raising the water level, which causes the fill valve to cut off again suddenly and the water in the tank to slosh around a bit. The sloshing water in turn causes the float to oscillate up and down, rapidly closing and then opening the valve very slightly with each oscillation of the water. And that causes the water hammer.

When you 'hear water like a "shhhhhhh" every so often', I think you're hearing the fill valve open up after enough water has leaked out of the tank past the flapper.

So I think you should first replace the flapper and leave everything else alone for a while to make sure that is the problem. You may also need to replace the fill valve, which has probably been somewhat abused by the water hammer, but I have found fill valves to be tricky on old toilets because the old tanks were a little differently shaped -- mine is so narrow no modern fill valve assembly would fit inside, and I had to cut the new valve assembly up and lash the shortened pieces together with cable ties.

Plus, the adjustable height feature of the generic replacement valve kit was a complete pain in th rear to get right. And I don't think I ever did get it quite right!
posted by jamjam at 11:36 PM on October 28, 2020 [1 favorite]

You have a couple good answers here, but I can't help but think there's maybe two things going on. Hearing the water "shhh" every so often I'd say is definitely linked to a leaky flapper. But the "terrible sound every few days" from "under your feet in the first floor bathroom" may be from a completely separate issue. Follow jamjam's advice and replace the flapper and fill valve (I haven't seen a fill valve with a ball on an arm in forever - yours must be old) then give it some time to see if the terrible noise goes away.
posted by achrise at 8:05 AM on October 29, 2020

If it's a regular bog standard flapper, they're super easy to replace and cheap.

The rental I moved into last year has the mansfield-style toilet (it's a circular ring with a central tower) and even replacing the gasket with a new one, there was always a slow drip.

Plumber's silicone grease resolved the issue; I removed the gasket, dried it out, smeared a thin layer of silicone grease (with a q-tip) on all of the surfaces of the gasket that touches something, refitted the gasket.

Et voila.
posted by porpoise at 1:34 PM on October 29, 2020

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