Does hot-water heater affect flow of cold water?

This am when I turned on my kitchen faucet, the flow of water stopped after five seconds or so. Same problem occurred in bathtub.

I checked in the basement, and the floor under the water heater is wet; obviously the water heater has a leak.

What I don’t understand: How does a leaky hot-water heater affect the flow of cold water? I guess I’d incorrectly assumed that there’s a “straight line” from outside water main, into house, then to faucet, bypassing the hot-water heater.

How does this work? Is this standard house plumbing design?

No such thing as a hot water heater. If it is hot water, it doesn’t need to be heated.
(heard that for years when I worked in a plumbing shop)

its called water heater a hot water heater could be a boiler system returning water is somewhat hot

Now that the snark is done: Usually, the main line comes into the house and there is a tee at some point. One leg of the tee feeds the WH and the other feeds the house’s cold water taps. I’m not a plumber, so I can’t speak to your problem of no water at the taps, but I don’t see how a leaky WH would cause your faucets not to work. Plumber time, before that tank ruptures and floods things.

Try turning on JUST the cold water. You are right that the cold water line comes in to your house and essentially goes right to the tap.
You, however, have leak in the system, when you turn on the (warm) water, some of that pressure is diverted to the hole in the water heater, which causes the pressure drop at the faucet.
So, like I said, try turning on the cold water only and you probably won’t have the problem. If you do, leave the handle right where it is, run down to the basement and see where the water is coming from. Maybe you’ll be lucky and it’s not coming from the heater itself and just a fitting above it.
After that experiment, look above the water heater, there’s two pipes, each one should have a shut off valve, close both of them. Soon. Leaks get bigger, not smaller and you have 60 PSI pushing against the hole trying to make a mess on your basement floor.

Joey P,

Are you sure about the two shut off valves? All of the homes that I have lived in either had one or none. I have not seen a shutoff valve on the hot water side. If you think about it, hot water expands. If it has nowhere to go, it will break something. You do not want to break your water heater. (This may be a moot point for LynnM, see below). Most modern homes, after 1990 or so, have a air-filled stand pipe, or they have an expansion tank, somewhere in the hot waterline. This allows the hot water to expand in the pipes or tank without breaking things.


If your water heater is electric, TURN OFF the electricity BEFORE you work on, or even look at the water heater. No electrocutions please! Water & electricity do not mix. Not good! No no no…

If you do indeed have two shutoff valves, just shut the cold water inlet off. You can tell which one is the cold one by feeling its temperature with your hands. Then you can try your sink. If it works OK, then you just need to replace your heater or fix the leak. If it does not work, (and you have two valves), try shutting off the hot water side for a long enough to test your sink. If the sink is now OK, the leak is much larger then you think. If the sink is still not working properly, then something else is also wrong with the plumbing. Now, turn off the heat on the heater. You really should turn off the heat and the water supply to the heater. Hot water spraying out of the heater in the basement is not a fun time. Trust me on this. I know!

I agree that you need to look closely at where the water is coming from. It may be all you need to replace is the over pressure valve on the water heater. It is an easy 10 minute job, which usually takes me at least an hour.:slight_smile:

Joey P is right, the leak will only get worse. Make sure you know where it is and then turn off the water to the water heater. You can now either fix it as a DIYer, or call a plumber and show the leaking place to him/her.

IHTH, 48.

there should be a shutoff valve on the hot water side before and after the hot water heater to allow its replacement. if you don’t have one before then you need to shut the whole house off to replace the heater. if you don’t have one after then you have to drain the whole hot water system to replace it. the heater itself should have a pressure relief valve so that both valves could be closed and it shouldn’t break the heater.