HomeWater Heater
  ■ Water heater Cleaning
It's advisable to clean the water heater at least once a year to prevent sediment build-up. Otherwise, minerals will make it difficult for the burner to heat the water, worse, potentially clog the pipes. Spring is the best season to clean the water heater.
shut off the valve (it is the cold water)
connect the hose to the drain valve and disconnect water line to prevent vacuum situation in the tank
open the drain valve and take out all the water until the sediment comes out
Though you may have drained all of the water, lots of sediment should still remain in the tank. Then you need to reconnect the water line and open the shut off valve of the water heater. The water will drop from the top of the tank to the bottom of it. The force of the dropping water should make the sediment rise from the bottom making it able to flow out of the drain valve.
Even after the above process, not all of the sediment will come out of the tank but it should be helpful for taking out more sediment.
If your drain valve is a plastic and old, there is a possibility of leaking after shutting the drain valve off. . If so, you have to replace the drain valve.

  ■ No Hot Water
when there is no hot water, please check the burner and pilot. If there is no fire on the pilot, you need to change the thermo coupler. Normally it is worn out after 3~4 years.

  ■ Combustion Air Requirment
Normally many people are installing the water heater at the garage. But sometimes, you need to install it inside of the house. If you have to install it inside of the house, you have to consider of sufficient amount of fresh air.
Code requires two cubic feet of o2 to one cubic feet of gas. If the capacity of gas water heater is 50,000BTU, need 2,500 cu ft of fresh air.
As you see in the picture, Code is requiring two of 100 sq. In. Net opening space for 40.000 BTU water heater.
Also these open spaces should be within 12” from the top and the bottom.
So if you install 40 gallons gas water heater at confined space, you need at least two of 125 sq. In. Net open space within 12” at the top and the bottom.

  ■ T&P Valve
Temperature and pressure relief valve (T&P valve) is required on all water heaters.
When the temperature is exceeded 210° F, T&P valve will be opened and release the hot water to control the inside temperature.
However, this valve is consumable and it would leak after 3~4 years.
If it is leaking, water will come out through the T&P valve drain pipe.
when it is leaking, you need to change it.

  ■ Water Heater Installation 
Disconnect inlet and outlet pipe and draining all water in the tank with opening drain valve at the lower side of water heater  
Take off the old straps.  
shut the gas valve off and disconnect the gas line. Now you can remove the old water heater.  
install new straps and 2" thick wood space bar. (water heater needs 2" gap from the wall) and set up the new water heater.  
connecting hot and cold water line with the flexible water lines. You need to install a valve at the cold water line side and connect the vent pipe. Also need to tighten 2 of straps.  
Installing a t&P valve drain. (3/4" pipe)  
this drawing is showing how to install a water heater at the garage.  
  ■ Tankless Water Heater
You need to consider following points before installation.

1. Check the capacity of the water heater.
    Sometimes if you are using more hot water than normal,
    you may need a bigger size than the normal capacity.
2. You need minimum 3/4" gas pipe size.
3. You need a vent pipe with double stainless steel wall
    because of hot vent gas.