Bath once was hot but now is not.

October 19, 2008 6:59 PM

Why is my bath not hot anymore?

My bathtub, which once filled so delightfully with steaming hot water, now fills only partway before the water gets cold. What hypotheses should I consider in diagnosing the problem?

The tub is located on the second story. The hot water knob behind the tub is open full-bore. The water heater, located in the basement, is electric and about 10 years old. The temperature and quantity of hot water elsewhere in the house seems unchanged.

posted by ottereroticist to home & garden (5 comments total)

You say the quantity of hot water elsewhere is unchanged, but how have you tested that?

A lot of electric water heaters have two elements, one at the bottom and one about half-way up. If the one on the bottom burns out, then the other works alone to heat the water, and it only really heats the top half of the tank. The bottom part of the tank will at best be luke-warm.

My guess would be that you have such a water heater and the bottom element is either dead or fouled with minerals. You need to get a plumber in to check it.
posted by Class Goat at 7:03 PM on October 19, 2008

Seconding Class Goat's info. We had the same thing happen to our electric water heater about the time it turned 10.
posted by clarkstonian at 7:26 PM on October 19, 2008

Thirding. I've worked on many a hot water heater, and things like this are only caused by two things: thermostat is dead or heating element is dead. On a very odd occasion, there's a third cause, and that's sediment covering the bottom element, but you'll only have that if you're on well water. Any of the above parts can be replaced without replacing the whole water heater. Get a plumber and they'll be able to diagnose.
posted by deezil at 8:16 PM on October 19, 2008

Another possibility is a defective dip tube. The dip tube is a pipe that moves incoming cold water from the top of the tank to the bottom. Dip tubes manufactured between 1993 and 1997 were made of a type of plastic that turned brittle and fell apart easily. White particles in the water is a sure sign of a dip tube failure. I had one fail within 2 or 3 years of installation, and another after 12 years. When the dip tube deteriorates, incoming cold water is quickly mixed with outgoing hot water, and the tub doesn't get as much hot water as it used to.

You can get a replacement dip tube at a plumbing supply house. I didn't have any luck at the big-box home stores. If you've done any plumbing you won't find it difficult to replace.
posted by Snerd at 8:43 PM on October 19, 2008

Turned out one of the heating elements was dead. Cost me a new water heater, but now I have hot baths. Thanks AskMe!
posted by ottereroticist at 7:44 AM on November 19, 2008