I sent the information about the shower/bathtub valves because these are adjustable mixing valves set at the factory to produce a hot/cold mixture of water which can be readjusted over a wide range with screwdriver settings of screws accessible under the coverplate of the valve. My respectful suggestions for the repair of the present situation are as follows: A) To determine the temperature of the hot water in the hot water tank: a) Turn off the electricity to the hot water heater b) with a small screw driver, reset the thermostat on the hot water heater to its original setting of 125 degrees c) turn off the drain to the hot water heater d) turn on the inflow to the hot water heater e) open a hot (left sided) faucet on all four bathroom sinks and on the kitchen sink. g) when all air has been purged from the how water pipes and (cold) water is flowing freely through the left sided (hot) faucet, turn off the kitchen sink and the four bathroom sink left sided (hot) faucets. g) At thirty minute intervals, measure, with a thermometer, the temperature of water flowing though one of the sink left sided (hot) faucets. h) If the water remains cold, go to "Repair Hot Water Heater" below. i) Otherwise record the steady hot temperature ultimately attained. B) If the hot water heater is functioning, then, to determine the settings of the mixing valves over the two bathtubs and in the two shower stalls: a) Turn the mixing valve fully clockwise, permit the water to run until it has reached maximum steady temperature, and compare this "mixed" temperature with the unmixed hot temperature measured at A)i) above. b) If the temperature recorded at B)a) is identical to the temperature recorded at A)i) the mixing valve is not diluting the hot water with cold water, and you must decide whether it's worth the trouble to try to adjust the thermostat in the hot water tank to a higher temperature as described below, or to quit while you are ahead. c) If the temperature recorded at B)a) is less that the temperature recorded at A)i) the mixing valve is diluting the hot water with cold water, and you must decide whether it's worth the trouble (and risk) to try to set the mixing valve to a higher temperature, or to quit while you are ahead. C) Repair Hot Water Heater If hot water heater does not produce hot water, I would a) Turn off electricity to hot water heater at the circuit breaker box. b) Open metal shell of hot water heater to expose connections. (see RUUD_PROE30M2RU95EC1_Manual.pdf attached) c) With voltmeter set to 240V AC or higher make sure that there was on d240103_04_hot_water_heater.png no voltage between 1 and 3; 1 and ground, 3 and ground, 2 and 4; 2 and ground, 4 and ground. Absent all voltage, I would set the meter to measure Ohms, and determine the resistance between the two wires, yellow and blue, to the upper heating element, and the resistance between the two wires, black and red, to the lower heating element. Each of these resistances should either be very low (18.75 Ohms) or very high (infinite) with circuit open. If the circuit is open, it means that the heating element is burned out. If the circuit is closed with the resistance very low (18.75 Ohms) it means that the heating element is intact but is not receiving power if the water remains cold. Look at attachment d240103_04_hot_water_heater.png There is next to an upper black box a label: UPPER TERMOSTAT & HIGH TEMP LIMIT (ECO) The upper part of the box shows a diagram of a circuit breaker connecting 1 with 2 and 3 with 4 when the temperature is low and opening (disconnecting) these connections when the temperature is high. The lower part of the upper black box is the diagram of a thermostat which directs current to the upper heating element when the uppper temperature is low, and to the lower element when the upper temperature has risen. With the power to the hot water tank turned off at the circuit breaker box the ohmmeter reading between the lower terminals 1 and 2 in the upper thermostat box should be zero, while the reading between terminals 1 and 4 should be infinite since the connection is open. (Hypothetically, if the power were removed from the hot water tank when it was hot, these readings might be reversed, the reading between 1 and 2 open, and the reading between 1 and 4 zero. The lower box contains the lower thermostat which interrupts the flow of current to the lower element when the temperature in the lower tank has risen. Here the resistance between 1 and 2 should be zero when the tank is cold, but it should be infinite - open circuit when the water is hot. Thus when the water in the tank is uniformly warm both upper and lower heating elements are turned off. Thus it is possible to determine which, the circuit breaker, the upper thermostat, the lower thermostat, the upper heating element or the lower heating element requires replacement. The individual parts are inexpensive, and a set of all five is available from Amazon for $36. https://www.amazon.com/water-heater-repair-kit/s?k=water+heater+repair+kit ==> Resetting the thermostats on the mixing valves: Caution: I have had a memorable experience with an attempt to reset the thermostat in the mixing valve of the 1st floor addition bathroom. While trying to find the adjustment screw the body of the valve was inadvertently opened, hot and cold water poured into the inside of the wall and into the basement, it was necessary to turn off both the hot and cold supply pipes. The sealing gasket, which is specially designed and sold by Kohler, had been damaged beyond repair, but fortunately I remembered having some loose packing material in the form of string, with which I replaced the broken gasket. Fortunately I managed to get a tight seal which has not leaked for at least five or six years. Therefore if you decided the mixing valves needed to be reset, you might negotiate with the plumber to inquire: a) whether he know how to to it, and how much he would charge. I, (of course) would do it myself. I would begin by identifying the number of the Simmons Valves (of which I had bought and installed four, which the plumber said he would use. Whether or not he actually did so, - who knows ? I would look for packing material which might have the number. Otherwise I would photograph the existing installation, remove the handle and the cover plate, and photograph the front face of the valve with all its screws. I would try to obtain adjustment instructions on the Internet or from the manufacturer. I might even buy such a valve from Home Depot with the intention of immediate return after I had identified the adjustment screws. A major difficulty might arise from the circumstance that the existing installation is not code-compliant, because the individual mixing valves cannot be isolated, and if ones efforts caused a leak, the entire water system would have to be drained. If I were still fully alive, I would install such individual shut-off valves for each of the four bathrooms, - but just as legislating from beyond the grave is impossible, so is plumbing.