We have a leak from the tub into the ceiling below. I'm pretty sure it's from the overflow drain, but as soon as the home warranty plumber heard this he said "oh, that's the problem, the overflow gasket is not designed to take that much water" and basically washed his hands of the issue (and emphasized his great experience as a master plumber vs. mine [none]).

But this sounds crazy to me: my expectation is that an overflow drain should be able to take as much water as will flow through it without leaking. I agree it may not be able to prevent the tub from overtopping, but I do expect it should not leak unless you're pointing a pressure washer nozzle through it or something.

So am I crazy, or is he?

  • I just looked at one set of documentation that label's it "Vent" and not "Overflow".. interesting. – Tyson Sep 1 '16 at 18:59
  • Contrariwise, this other random guy on the internet (in response to the same link as in my answer below) basically says "yeah, interesting, but a lot of them are called overflows and if you install them right they work". Definitely seems like a bit of a mess... – eclarkso Sep 1 '16 at 19:08

Wow, he might be right... according to this, "overflow drains" are a complete misnomer and the whole assembly is YMMV/at your own risk/a farce:

According to PMI (Plumbing Manufacturers Institute) no manufacturer currently makes bathtub overflows, only trip lever assemblies are made.


If you disagree then I challenge you to come up with the documentation that these so called overflows are a real plumbing product in the same sense as any other plumbing product being what it claims to be:

• Show that a standards specification exists with ASME, ANSI, NSF, IAPMO, or any other approved standards making group.

• Show the documentation for the engineering calculations that specify the flow rates the overflow should be capable of handling and how this relates to the overflow "protecting against accidental flooding resulting from an unattended filling operation".

• Show what listing agency is providing a listing for such a product and what testing protocol they are using to verify that the overflow is meeting the standard.

• Show what manufacturer makes an overflow that has such a listing and stands behind the product with a warranty that the product will "protect against accidental flooding resulting from an unattended filling operation" according to the standard to which it is listed.

You will find that none of this exists.


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  • FWIW, I really hope someone else comes along with a (legit) answer I'd rather hear! – eclarkso Sep 1 '16 at 19:36
  • I think the YMMV comment is the most apt: I've seen plenty of failures because the parts haven't been lined up correctly. Similarly, I've seen plenty of perfectly functional units. Maybe the take-home message is that you shouldn't rely on the overflow. – Aloysius Defenestrate Sep 2 '16 at 1:24
  • Given what I've learned, I can definitely believe it's YMMV in terms of part and/or install quality (and deterioration over time). What I still take issue with (from my plumber that prompted the question) is the idea that there is no correct installation possible and you should expect them all to leak with any amount of water going through them. – eclarkso Sep 2 '16 at 1:56

no manufacturer currently makes bathtub overflows, only trip lever assemblies are made.

Well, on this side of the pond, bathtub manufacturers describe items such as "BATH EXTENDED POP UP WASTE & OVERFLOW" and "BATH WASTE AND OVERFLOW"

These items are sold as overflows. I'm pretty sure that if a vendor describes something as an overflow, or a plumber installs something they describe as an overflow, they can be prosecuted if it is a deliberately misleading term.

The statutory right under section 9 (goods to be of satisfactory quality) will only be breached if goods are not of the standard which a reasonable person would consider to be satisfactory, taking into account circumstances including the price and any description given.

- http://www.legislation.gov.uk/ukpga/2015/15/notes

If something described as an "overflow" leaks, I believe a reasonable person would consider that unsatisfactory. IANAL.

Just because there are no government mandated rules or standards covering a specific item does not mean that manufacturers, vendors and installers are free to use misleading words to deceive the public and/or to supply or install plumbing that leaks.

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