The same defect happened to me a few years ago on my gas water heater. I noted the Navien 240S would turn off the flame (at least … My tankless heater turns cold after 10 minutes in all showers. Tried a new shower head again but no luck. Well, let’s get the obvious out of the way: Has your family grown? It doesn't happen every time though. Now it is back. The Wall. Had a pipe burst in the wall, turned water off to water heater and whole house. tried flushing with vinegar, - Answered by a verified Plumber It is less than three years old. You see, some dip tubes (especially ones on older water heaters) are prone to breaking, which allows cold water to mix with the hot water at the top of your tank. My Hot Water Turns Cold After a Few Minutes. I'd say cold would be gradual descent from hot to warm to cold so we can at least get out of the shower water and ~20 seconds later it goes back up and stays that way for 2-3 minutes then repeats. Water Heater Problems. A tepid or cold stream of water may be an indication that your water heater is not set to the right temperature. Then it returns to normal hot water and stays that way until I'm done. Extreme care should be used at all times to avoid contact with energized components inside the furnace. So what’s the deal? Water goes cold on my rinnai tankless, after 3 or 4 minutes, then gets hot then goes cold. Water heater repair is a delicate task. Water heater repair is a delicate task. Indirect heat. But all of a sudden, it seems like your home’s hot water supply turns cold a lot faster than usual— sometimes even after just a few minutes of use. When showering, the Titan water heater went ice cold after a few minutes then hot and then cold again, what is the problem? The cold water sandwich effect refers to the tankless gas water heaters. The guidelines for most tank heaters recommend a water temperature of 120 degrees. I thought maybe the flow was insufficient (the RUC98i is way over-specced for our humble home), so I tried turning on the hot water faucet in the sink while I shower. The necessary repairs are often difficult, requiring high levels of skill and expertise. What To Do If Your Hot Water Turns Cold After A Few Minutes. I noted the Navien 240S would turn off the flame (at least on the LCD) for ~20 seconds, then fire back up, over and over. If so, you may just need a larger tank. In all cases, tankless water heaters must be property vented. Sign In; Main Site; Store; Discussions; Activity; Best Of... Home › Domestic Hot Water. Starts out hot always but gets cold within seconds. Then it returns to normal hot water and stays that way until I'm done. However, when the tap is turned off, so too is the hot water supply. I suspect if you had the shower set to totally hot, you'd just notice reduced flow. Click here to Find a Contractor in your area. The cold water will eventually turn to hot after a few minutes. But here are the strange things I noticed. The shower has one knob that controls the temperature and water flow so I assumed there was something inside the control that has worn out and is biasing things towards the cold water. First off, this is a common tankless problem called a “cold water sandwich”. I'd say cold would be gradual descent from hot to warm to cold so we can at least get out of the shower water and ~20 seconds later it goes back up and stays that way for 2-3 minutes then repeats. This problem happens because the heat exchanger (the part that actually heats the water) takes a while to warm up. At first we thought it was the water heater as the culprit, but it seems to be more complicated than that. Here is a quick way to solve any hot water shower troubles. That did not help, the water still went dead cold after about 5 minutes.
Had this problem 4 years ago and I put in a new shower head and it worked. Make a seemingly simple mistake and it can easily turn into a costly disaster. No one else is in the house using hot water, so that's not it. First off, this is a common tankless problem called a “cold water sandwich”. Life expectancy is 10-15 years. After a few seconds, say 10-20, of decent hot water, it turns completely cold for another 10-20 seconds, even if I max out the control. If she turns on the hot water in the sink right next to the shower the water is still hot. The necessary repairs are often difficult, requiring high levels of skill and expertise.

Water starts out cold, gets warm for a few seconds, then goes cold again and continues that way.

First, check all your fixtures throughout the house to see if your cold water shower is a singular problem or a whole-house situation. If this is the problem, then there are really 2 solutions here.