Q. I live in a 1958 rambler. My problem is getting hot water in both the master shower and the hall bathroom shower. When the hot water is turned all the way on in either bathroom, only lukewarm water comes out of the shower. In the master bathroom, if you flush the toilet, the shower water becomes hot. In the hall bathroom, if you turn on the hot water in the sink, the water in that shower turns hot, while the sink water remains cold, though without the shower on, the sink hot water works just fine. All other hot water faucets work. Both a handyman and a plumber have been puzzled by my problem. Where should I turn next?


A. There could be a cross-connection somewhere, allowing hot and cold water to mix within the pipes, says Seth Kramer, service manager at Kramer & Sons Plumbing in Alexandria. Kramer has seen instances where a cross-connection happened because a hand sprayer in a shower was turned on and off without using the main shower control. So if you have a hand sprayer, try using the main controls and see if that solves your puzzle. If not, call in a second plumber to help with the detective work. A cross-connection could be occurring because the pipes were installed incorrectly (most likely if temperature fluctuations have always been a problem in your house) or because a mixing valve in a faucet or at your washing machine has failed (more likely if the problem is new).

It’s also possible that several different problems are occurring simultaneously. By tracing which faucets deliver hot water first, a good plumber can sometimes figure out how the pipes are linked, even if the piping isn’t easily accessible. The pipes may be undersize, and the solution could involve installing a pressure-balancing shower valve or an in-line pressure-balancing valve. These are often called anti-scald valves because they adjust flow to make sure water doesn’t suddenly get too hot. (For safety reasons, they’re now required in new construction.)

Plumbers typically charge for service calls, rather than give free estimates. Kramer’s company (703-360-6400, www.kramerandsonsplumbing.com) charges $49, which covers travel and diagnostic time. If you need either kind of pressure-balancing valve, expect to pay $500 to $800. That covers the valve itself, which is hidden in the wall, as well as new visible parts, including the shower head, tub spout and controls.

E-mail localliving@washpost.com with your home-improvement questions.