LESLIE: Brad in Tennessee is on the line with a home that probably has the best practical joke already built into it: you flush the toilet, the shower gets cold. Why do you want to change that?
BRAD: Well, because my four-year-old son seems to think it’s more of a joke than it’s a real thing.
TOM: Than his parents?
BRAD: Yes. That is the problem.
TOM: Alright. So the shower valve itself, right? There’s an easy solution to this, first of all, Brad. It requires you to change the shower valve into something called a pressure-balanced valve. Now, I know you don’t have a pressure-balanced valve because your water temperature’s changing when you draw off water, in this case, by flushing the toilet. It would probably also happen if you ran other fixtures in the house. But it’s because you have a differential in the pressure or the mix, as you say, between the hot and the cold.
What a pressure-balanced valve does is it keeps that mix the same and regardless of what happens to either the cold-water supply or the hot-water supply. So you can have more or less of either temperature of water but the ratio of the mix together doesn’t change. You may get less pressure when you flush that toilet after this valve’s installed but it won’t be a shock, OK? It won’t change the temperature dramatically. That’s what a pressure-balanced valve does and it sounds like you don’t have one and that would be the solution.
BRAD: Excellent, excellent. Well, I will run out and get one.
TOM: Alright. It’s a bit of a project. You may not be able to install it yourself. It’s pretty much you have to re-plumb the shower valve there. You may need a plumber to help you but it definitely will solve this.
BRAD: OK. Well, excellent. We found out where to start now and where the joke ends.