Starting with the first shower in the morning the water will start hot and then cool down within three or four minutes. We have a Mixet single handle faucet in the shower, and a 50 gallon Reliance 850 water heater set as high at it will go (we have no children living at home and are not worried about scalding water). The shower head is a large Speakman Anystream with the aerator removed. Swing the handle of the faucet to the left for hot and swing to the right for cold. As the shower water starts to cool down from its hot, we move the handle further to the left and it does not get any warmer. We have tried turning the water flow higher and lower without avail. How can we keep the water at a constant hot temperature for at least ten minutes? Any suggestions would be appreciated. If you think the valve/faucet might have something to do with it, what would you recommend as a replacement?
Thank you and looking forward to your response.

Reliance 850 or do you mean 805? Reliance Water Heaters | Where to Buy Try this to get a manual, your probklem could be caused by a bad dip tube which is easy and cheap to replace.

Usually when water will not stay hot for very long it means there is a break or leak in the inlet pipe that delivers new cold water into the water heater. The pipe is supposed to deliver the new cold water to the bottom of the tank and the hot water then rises to the top where the outlet to the bath is. If the pipe is leaking cold water at the top of the tank, it will mix with the hot water and quickly cool everything down. The cold inlet into the water heater goes to the bottom, and the hot return extracts from the top and is a shorter pipe. You would have to shut off both the cold inlet and the hot outlet and drain a little out of the tank so you can unsolder the cold pipe and then unscrew it to check if its good. Most new tanks have a plastic inlet pipe that goes to the bottom, and if its not seated correctly or it breaks you get short hot water. Also you would want to unsolder from fairly high to avoid melting the plastic tube, and when replacing it, wrap a cool wet towel around the base of the metal pipe to keep from melting the new plastic tube when your re-soldering above it. Some cold lines have an extra valve and pipe you can use to let air in so the soldering goes smoothly. One thing though, I always buy an new drain tap for the bottom of the tank. Once you open them after a few years, they do not like to close properly and will leak.

Hi Appzalien...

That "inlet tube" is called a DIP TUBE which ballenger mentioned in his post, above. The issue could certainly be that and you have described removal pretty good here... ;)

I'm also thinking that because WPBROWN said, "50 gallon Reliance 850 water heater set as high at it will go " that we could have an issue with the gas valve (thermostat) itself. Here, setting a water heater up to maximum and only getting hot water as described would certainly suggest that there are issues with this heater.

Wpbrown... I would recommend that you call the manufacturer of the water heater and talk to their technical department and see what they think here... could be the gas valve or the dip tube and there is no reason to guess here... they will tell you steps to take to test all and they may very well send you the parts under warranty IF the heater is relatively new.

Hey! Post back with questions, OK?

Mark

I haven't done a water heater since 1995, so "Dip Tube" just wasn't in my memories vocabulary anymore. Once it was mentioned I remembered. There is also the metal rod that determines the life of the tank (warranty period). It prevents electrolysis and keeps the tank from rusting. I was told that if you buy a 10year water heater, often the only difference between it and the 15 or 20 year is the length of that rod or number of rods. So if you buy a ten year tank and change the rod after 8 or 9 years you can get the benefit of a longer tank. And putting a longer rod in the second time if you can get one can give you 15 more.

Anode Rod, I looked it up. (sacrificial anode)

Nice to know if your going to drain the tank for cleaning. Replacing the drain valve is a good idea too, since they have a tendency to leak when used after a few years sitting.

Many water heater manufacturers received a bad batch of plastic dip tubes some years ago, many of them still offer a free replacement dip tube and a few even offer to pay a plumber to install. Worth calling Reliance to see where they stand if it turns out to be the dip tube. I usually buy and install 10 year tankd, if they are at my house they get a new anode on their 10th birthday, just as a little treat to them and me. http://www.diptube.info/DipTube3ColdShower.html