Funny-tasting tap water

A couple weeks ago, my daughter pointed out one morning that our tap water tasted funny. It was alkaline, soapy, and so strong that occasionally the taste burned my throat. NOT chlorine-y.

I asked the city to come and test, which they do at the point the water comes into the house. They said everything was within their limits and that they hadn’t recently added anything to the water. I’ve dealt with them before and am inclined to trust them.

We drank bottled water for a while, hoping it would clear up. It has lessened, but not gone away. I use a Brita carafe (changed filter recently) and that has no effect.

Here’s the weird thing. Initially the taste seemed to be present right away out of the tap. Now, it seems to develop over time. Water straight from the tap or right out of the Brita tastes okay. But after some hours–for example, if I drink from my bedside cup in the morning–the alkaline flavor is there.

For a brief time I thought maybe it was dishwasher soap residue on our plastic cups, built up after many washings. But brand new plastic cups, washed only once by hand, exhibit the same behavior. So do glass cups–water from tap and Brita taste fine at night, soapy in the morning.

What’s going on here?

Are there snakes in your pipes?
Jokes aside, if the problem isn’t with the city then the problem is either in your pipes or your water tank. If you live in a house and can have it checked out you probably should. Things can get in there and die
Does hot or cold water from the faucet affect the flavor or appearance of the water? That could be an indicator of your problem.
Have you tried boiling the water and seeing if it leaves a residue or if it still has the odd flavor issue?

Do you have a water softener, or ion-exchange/activated charcoal system?

if you fill a container with water it initially tastes OK but after sitting develops a taste?

The city should be giving you the ‘straight dope’ but the only thing that comes to mind for me is there may be a malfunctioning backflow prevention device on a boiler upstream from you.

Have you asked any of your neighbors if they have notice the same thing?