Frequently Asked Questions

What is the efficiency rating of my water heater?

Bock Models 32E and 33E are classified by the Department of Energy as residential water heaters and are rated by an Energy Factor (EF) ranging from .66 to .68. Industry average is .58. The higher the EF, the more the heater transfers energy to the water using less energy.

For the Model 40 and higher - these models are classified as commercial heaters and are rated by thermal efficiency. Bock heaters are rated 80% or higher depending on the specific model. Industry average is 78%.

For additional information check out the Air-Conditioning, Heating, and Refrigeration Institute (AHRI) website at

How often should maintenance be performed on my heater?

Bock recommends that water heaters – oil or gas, should be maintained on an annual basis. This maintenance should be performed by a qualified technician.

What type of maintenance should be performed?

1.Drain and flush heater of all sediment.
2.Inspect and replace anode rods.
3.Brush and clean flue passages and chamber area.
4.Clean and service oil or gas burners and replace filter (oil only).
5.Clean and inspect flue piping and seal all joints.
6.Check and test all controls for safety and proper operation.
7.Adjust burner for proper operation and maximum efficiency using combustion testing instrument.
This should only be done by a qualified service technician.

What are anode rods and why should they be replaced?

Anode rods protect the interior (water side) of the water heater from the process of electrolysis (stray current found in every structure), and prevent premature failure of the water heater. Failure to replace anode rods may void your warranty.

Does my Bock indirect water heater have anode rods?

Yes. The Model CT 30, 40, and 50 has one magnesium anode rod directly in the center of the heater. The Model 80 and 119 CT have two rods. The SK models all have two anode rods.

What materials are used in anode rods?

All Bock water heaters are shipped from our plant with magnesium anode rods. Aluminum rods are available upon request.

Are all anode rods the same?

No. Our rods are specifically manufactured to our specifications and are almost twice the thickness of standard or generic rods. They also come in various pipe sizes (3/4” or 1”) and lengths depending on the model heater you have. Link rods are also available upon request. Link rods may be used in the event the clearance from the top of the water heater to the ceiling will not permit standard length rods (minimum length is 30”).

What is causing the “rotten egg” smell from my hot water?

The smell is hydrogen sulfide and generally occurs when the water supply to the structure is from a well system. Bacteria from the well or water supply reacts with the magnesium anode rod or rods and creates hydrogen sulfide. If this occurs, the water heater will have to be drained and flushed with a chlorine solution which will kill the bacteria. The magnesium rods will have to be replaced with aluminum rods. If the smell persists it may be necessary to have your water supply tested and appropriate action taken.

What causes the popping sound from the inside of the heater when it’s in operation?

The sound is an indication that mineral / lime deposits have built up on the bottom of the heater. Suggest flushing the tank (see maintenance procedures). If this does not help the interior of the tank will have to be professionally cleaned. Remember that this buildup may cause premature tank failure.

Getting rusty hot water?

There are a number of causes. Iron and minerals brought in from the cold water supply have built up in the water heater is most common. It could also mean that the anode rods have been compromised and electrolysis is attacking the tank interior. Suggest flushing the heater and inspect and/or replace anode rods. If the condition persists, filtration on the cold water supply may be necessary. If this condition persists, the heater may have to be replaced.

Why do I get a burst of air when I open a hot water fixture?

It may be coming from you cold water supply if you are on a well system. If this is the case you should contact you plumber. It could also be electrolysis (stray current) which is eating away the anode rods at a very rapid rate which forms a gas in the top of the heater. This may be caused by an improperly grounded water heater or a compromised earth ground in the structure.

What causes the reduction of hot water from my heater?

The reduction may be caused by three primary reasons. This could be caused by an improperly tuned burner. This will also occur when the cold water dip tube has been compromised. Dip tubes do require replacement after a period of years, especially when the supply water has a higher than normal levels of chlorine. The third cause is sediment or lime deposits which have accumulated on the bottom of the tank. This accumulation acts as a barrier or insulator between the burner and the water which requires more energy to heat the water. Every half inch of sediment on the bottom of the heater will require 60 to 70% more fuel to heat the water.

My T&P (temperature and pressure relief) valve is dripping water?

This is caused by either excessive incoming water pressure (40 to 70 psi is normal), or the system is a closed loop system which requires an expansion tank devise. T&P valves could at times release water due to excessive water temperature in the water heater (above 210°F/99°C). Check the aquastat setting. If this fails to correct the condition contact you local plumber or service company. Please remember that water temperatures above 120°F can cause scalding.

Can I install a Bock Water Heater myself?

Bock Water Heaters should be installed and properly adjusted by a plumbing and heating professional. There are National and local codes and safety requirements that pertain to water heater installations and without the knowledge of these requirements you could be in violation of these codes as well as endangering yourself and your family.

My burner keeps going on safety / lockout – have to hit the reset?

The best thing to do is to contact your local service company or installer.

Can I use an insulation blanket around my heater to improve efficiency?

Insulation blankets will not improve efficiency or reduce standby loss and must not be used on oil or gas fired water heaters as they create a fire hazard.

For additional questions please contact your local licensed service provider.