I hope you listened to me last month when we were talking about cleaning a coil to get better hot water. This works in probably 90 percent of the jobs I worked on. But the other 10 percent needed a new coil OR another appliance to deliver hot water. But even those can get you in “hot water” (pardon the pun).
There is going to be a time when you have a customer that tells you there is no or not enough hot water from a water heater or a storage tank. Let me start by saying that if the water tank you have has the cold water entering the bottom of the tank and the hot water exiting the top, you should not have the problem I am going to describe here. In a very many cases you will have a tank where both the cold water and the hot water enter and exit through the top of the tank. If this is the case and you get only a little very hot water then it rapidly cools off, suspect the dip tube.
The dip tube is located inside the tank and brings the cold water down inside the tank to a location near the aquastat. When your customer opens a faucet for hot water, the cold water enters the tank through the dip tube and forces the hot water out of the top opening. It really has everything to do with pressures. Now, what do you suppose would happen if that dip tube were to break off inside the tank? Well, the cold water would mix with the hot water at the top of the tank, right? The water never gets to cool the tank down and the aquastst would never feel any temperature change, right? No temperature change, the aquastat will not tell the heat source to come on. The cold water will take the shortest path, which means it will go straight out into the “hot water” piping and the next thing you will hear is a scream as the cold water hits the warm body that is expecting a nice hot shower.
What I would check first is to ask the customer to run the water out of the hot water faucet AFTER I have got into the basement. I would ask them to wait at the top of the stairs, and when I am ready, I would tell them to go ahead. I, of course, am at the water heater at this time with my hands on the hot and cold piping. As soon as the faucet is opened, the cold water pipe should get cold and the hot water piping should get hot. If in a minute both piping is cold, the dip tube is my prime suspect. Sometimes the manufacturers made it easy for us. If you shut off the cold water supply and drain the water down below the lever of the T&P valve, you may be able to remove the T&P valve and using a good flashlight, look into the tank and see the tube. If you can’t see it, I would take a wire coat hanger and break it apart so I could make a feeler probe. If you put a curved bend on the hanger, you can insert the hanger into the tank, but don’t lose it in there, and feel around for the tube. If you feel nothing, the tube is gone.
What you do now is open for discussion! Some technicians will fabricate a dip tube, and after cutting the cold water piping, will insert it into the cold water tapping on the tank and then re-connect the cold water piping. This works, just make sure the length of your new dip tube is the correct length. Personally, I know of no manufacturer that would cover the tank in the event of a tank failure using the method, but I would go to a supply house (or my van) and get a replacement dip tube and re-install it in the water heater. AND CHARGE THE CUSTOMER! If the unit is under manufacturer’s warrantee, they will pay you to repair it correctly. How you handle it is up to you, but remember, as far as the customer is concerned YOU are the expert!
Being an expert puts a burden on you as well as praise. I was declared an expert a few times by the court system, but I never thought of myself as one. Edwin L. Drake is one of my hero’s and he dealt with experts back in 1859. Know it or not, you owe a great deal to him! He is the man who sank the first oil well in Titusville, Pennsylvania. The oil well Drake constructed was called "Drake's Folly." When Drake asked the “expert drillers” to work with him, most said “Drill for oil? You mean drill into the ground to try and find oil? You’re crazy.” At a slow progress, three feet a day, his well kept going deeper and deeper, until, on August 27, 1859, it reached a depth of 69 feet. Drake had struck oil, black gold, and created the industry you and I work in today. Thanks Edwin.