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<p>If you are having<b> trouble with the temperatures</b> of your <b>gas hot water heater</b> fluctuating too much, or after <b>changing the thermocouple</b> of your gas <b>hot water heater</b> then you may need to change the complete <b>gas valve and thermostat assembly</b>. Also if you have changed the <b>thermocouple</b> and the pilot still will not stay lit, then the gas valve could be bad or the <b>ECO (Emergency Cutout)</b> may have activated and is open. This is a onetime device and cannot be replaced.<br />
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<p>These instructions are for the older style <b>gas valve and thermostat combination</b>. These commonly have a large red knob that adjusts the temperature of the water. Also note that the burner tube nut for <b>natural gas</b> is right hand thread, but if you have <b>LP or propane gas</b> the burner tube nut is left hand thread.<br />
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<p>The newer <b>gas valve thermostat combinations</b> that have come out recently are similar, but they have a well in the tank that the sensor slides into. The assembly is held fast with a set screw. With this type of <b>gas valve and thermostat unit </b>the tank does not need to be drained, but most of the rest of the change out is similar.<br /><br />To change a <b>gas hot water heater thermostat</b> you will need to first buy a new gas valve for your <b>hot water heater</b>. The <b>gas valve</b> and the <b>thermostat</b> are integrated into one unit.<br /><br />To <b>replace the thermostat on a gas hot water heater</b> you must follow these procedures....<br /><br />1. Turn off the incoming water and<b> drain the hot water heater</b>.<br /><br />2. Remove the <b>pilot tube</b>, the <b>burner gas tube</b> and the thermocouple from the gas valve. Turn off the <b>gas line</b> and remove from the gas valve.<br /><br />3. Get a <b>pump pliers</b> or a<b> wrench</b> in behind the gas valve and turn the whole assembly CCW to remove it from the tank.<br /><br />4. After applying pipe dope or tape to the new gas valve threads, turn the new gas valve into the tank by turning in a CW direction. Be careful not to damage the small wires to the <b>ECO</b>. They are the little red wires on the back. If you break them the assembly is irreparably damaged.<br /><br />5. Reinstall the gas line, thermocouple, burner tube, and the pilot tube to the gas valve.<br /><br />6. Fill tank with water. Make sure to open a <b>hot water faucet</b> and <b>purge all air from the tank.<br /><br /></b>7. <b>Check for leaks</b> where the gas line hooks up with soapy water.<br /><br />8. Relight pilot light and check operation.<br /><br />9. Set the new temperature setting to a medium setting and then adjust the temperature to your liking from there and adequate time for heating completely<br />
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check your water pressure and then make sure it is not to high or all the problems you have had were not the answer. it is a pressure /temperature valve not just . temp.
Replace gas control valve. The gas valve is the thermostat.
Vacation setting should be 50 degrees, or so, depending on exact gas control valve. If gas water heater is not responding to temperature setting, then thermostat is suspect.
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The drain valve can always be replaced so you can drain that with no worries....after it is empty open and clsoe the cold water valve to flush more...
As far as being large enough... that depends...
If you have a teenager like I do that takes 40 min showers in steaming hot water... no....
If you are running more then one shower at a time... then probably not...
The other thing that could have happened is that the dip tube for the cold water inlet has broken off or disintergrated...that happens...
Usually you will then get cold water and the gas valve will not yet have kicked on the burner, because the cold water is not going to the bottom...
If it is a new install... check thet the supply and return are hooked up correctly...
thermostat is gas vavle may also be bad, but not too likely...
The first thing I would do is turn up temp control on gas valve.Control is located on front of gas valve at the bottom front of heater.They usually have a indicator dial on front with an arrow pointing direction.Turn dial to higher setting when burner is not on and this should turn burner on and provide hotter water. The control is normally turned clockwise to increase temperature.If control is already turned all the way up then water heater may need to be replaced.Depending on water quality in your area heater may have a large amount of mineral build up and it may not be capable of producing enough or hot enough water. If this the case all I can suggest is to try to drain tank and flush some of the deposits out. If you have installation manual it will give you instructions on how to do this. If not see if you have working shut off valve on cold water line ,if it works shut it off and connect drain hose to drain valve on bottom right side of gas valve. Put hose to floor drain or sump basin if you have one. Turn control knob on top of gas valve from on to pilot,this will leave pilot light on but prevent burner from working while draining. Open drain valve ,flow rate may be slow or not at all. Open hot water side of some faucet to provide air to help draining. You may try opening water supply valve to heater a few times to aid in draining. If you can get it to drain,shut drain valve off when done,turn cold water supply back on and shut off hot water outlet. Then when tank is full open hot water vavle to bleed air out of heater and piping. Turn control knob on top of gas valve back to on position. This should bring burner back on .It will take about 1/2 hour to heat. If you can't get it to drain or this doesn't help you might consider getting a new 40 gallon heater. Hope this helps. Thanks
if you are using a mixing valve it is pre set so as to not burn your self but if you wish to set it on the dial depending on which one you have, some are flat tip screw driver some have plastic cap on it turn on the water and set to your desired temp by turning clock wise or counter clock wise
If the pilot light stays on, the thermocouple and pilot flame are good. If you turn the control to "on" and turn up the thermostatic control knob to call for heating and get nothing else then the control (gas valve, thermostatic control) is bad. The control can be replaced - they are mostly generic except for gas type - but they are not cheap and if the control is bad the tank is probably not far behind (changing the control could cause it to leak). Unless the water heater is less than 3-5 years old, replace the whole thing!
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