Rheem RTGH-RH11DV Use And Care Manual page 80

Flushing the Water Heater
Flushing the heat exchanger is a complicated procedure that should only be performed by a qualified service technician.
NOTE: Improper maintenance WILL VOID water heater warranty.
1. Disconnect electrical power to the water heater.
2. Close the shutoff valves on both hot water outlet and cold water inlet lines (V1 and V2). See Figure 57.
3. Connect one hose (D1, Figure 57) to the valve (V3) and place the free end in a bucket. Connect one of the hoses (D3) to the circulation pump
outlet and the cold water inlet line to valve V4. Connect the other hose (D2) to the circulation pump inlet and place the free end in the bucket.
V3
Figure 57 – Flushing the Water Heater
4. Pour tankless water heater cleaning solution into the bucket. Ensure the cleaning solution is approved for potable water systems. Place the
drain hose (D1) and hose D2 to the pump inlet in the cleaning solution.
5. Open service valves (V3 and V4) on the hot water outlet and cold water inlet lines.
6. Turn on the circulation pump. Operate the pump and allow the cleaning solution to circulate through the water heater for at least 1 hour at a
rate of 4 gallons per minute. This will remove any possible harmful scale deposits.
7. Rinse the cleaning solution from the combination water heater as follows:
a. Remove the free end of drain hose D1 from the bucket.
b. Close service valve V4 and open shutoff valve V2.
c. Do not open shutoff valve V1.
d. Allow water to flow through the water heater for 5 minutes.
e. Close shutoff valve V2.
8. Disconnect all hoses.
9. Remove the cold water inlet filter from the water heater and clean out any residues.
10. Reinsert the filter and ensure the filter cap is securely tightened.
11. Connect electrical power to the water heater.
12. Open a hot water faucet. Run the water heater continuously for five minutes to ensure all cleaning solution is purged from the system.
Check for leaks and ensure the water heater is operating properly.
V4
V1
V2
D1
D2
80
D3
AP18733 REV. 3.2.17