water heater code

[Robert Gaspy]

I would like to share my questions regarding water heater in GARAGE installation.

If ELECTRICAL water heater installed in the GARAGE ( NOT in the house ) does it mandatory needs a pan underneath?

Water heater is on the 2 inch pad now . Water heater is 24 inches roud and pad is 24 inches also - is it per code or needs to have 26 inches pad?

Pan is 24 inches also - is it per code or needs to have 26 inches pan?

Drain (pressure valve pipe )is now directly down to the concrete floor in the garage - is it per code or needs to be drained out through the wall?

I appreciate your thoughts and advises

[Alton Darty]

In garages a pan should not be required as it is probably not in an area where damage to finishes would occur. A platform to raise the lower heating element above 18" is usually required when a water heater is installed in a garage.

From the 2009 IRC
P2801.5 Required pan. Where water heaters or hot water storage
tanks are installed in locations where leakage of the tanks
or connections will cause damage, the tank or water heater shall
be installed in a galvanized steel pan having a material thickness
of not less than 0.0236 inch (0.6010 mm) (No. 24 gage), or
other pans approved for such use.

P2801.6 Water heaters installed in garages. Water heaters
having an ignition source shall be elevated such that the source
of ignition is not less than 18 inches (457 mm) above the garage
floor.

A lot will depend on the AHJ, practices will also vary from state to state, and even regions within a state. I would prefer to see the TPR drain terminate at the exterior through an air gap but many AHJs will allow TPR discharge to drain to the garage floor.

[Robert Gaspy]

Thank you very much Alton! Very good explanation.

This garage does NOT have a drain - should it be reqired mandatory to drain TPR to outside ? or it can simply drain on the garage floor , as it is concrete floor?



In garages a pan should not be required as it is probably not in an area where damage to finishes would occur. A platform to raise the lower heating element above 18" is usually required when a water heater is installed in a garage.

From the 2009 IRC
P2801.5 Required pan. Where water heaters or hot water storage
tanks are installed in locations where leakage of the tanks
or connections will cause damage, the tank or water heater shall
be installed in a galvanized steel pan having a material thickness
of not less than 0.0236 inch (0.6010 mm) (No. 24 gage), or
other pans approved for such use.

P2801.6 Water heaters installed in garages. Water heaters
having an ignition source shall be elevated such that the source
of ignition is not less than 18 inches (457 mm) above the garage
floor.

A lot will depend on the AHJ, practices will also vary from state to state, and even regions within a state. I would prefer to see the TPR drain terminate at the exterior through an air gap but many AHJs will allow TPR discharge to drain to the garage floor.

[Marc M]

608.5 Relief valves located inside a building shall be provided
with a drain, not smaller than the relief valve outlet, of galvanized
steel, hard-drawn copper piping and fittings, CPVC or
listed relief valve drain tube with fittings that will not reduce
the internal bore of the pipe or tubing (straight lengths as opposed
to coils) and shall extend fromthe valve to the outside of
the building, with the end of the pipe not more than two (2)
feet (610 mm) nor less than six (6) inches (152 mm) above
ground or the flood level of the area receiving the discharge
and pointing downward. Such drains shall be permitted to terminate
at other approved locations. Relief valve drains shall
not terminate in a building’s crawl space. No part of such drain
pipe shall be trapped or subject to freezing. The terminal end of
the drain pipe shall not be threaded.

[Jerry Peck]

The IRC, and most codes using the IRC as their base code, require the T&P discharge pipe to discharge (end) in the same room or space as the water heater is located in.

Many water heaters have warnings (on labels and/or in their installation instructions) not to install the water heater in a garage ... most give conditions which need to be met, some seem to leave it at 'don't do it' without specifically stating 'don't do it'.

It's all in the wording in the labels and installation instructions.

[Bob Harper]

The discharge from a relief valve should occur where it can be witnessed. If it discharges outdoors in the flower bed, the owner won't realize there is a problem.

[Jerry Peck]

There are two basic schools of thought on the discharge from a water heater T&Park relief valve - when a T&P relief valve discharges it may be an indication of a fault with the water heater (excluding a leaking T&P relief valve). That indicated failure is the water heater failing to stop heating - which can create a boiler bomb being made.

Both schools of thought are based on the fact that the occupants need to know that something is wrong with the water heater - the method of letting the occupants know is different.

- One school of thought is to install the water heater in the middle of the dining room and any discharge from the T&P will be seen ... but water heaters are not installed in the middle of dining rooms are they ... water heaters are installed in out of the way locations (this is not factored into this school of thought's reasoning) ... which ends up with the discharge being in that same out of the way location. Seems counterproductive and counterintuitive - but most codes are written that way.

- Another school of thought is to discharge the T&P discharge directly to the outdoors (most, if not all, codes used to be this way). With the T&P discharging under the described fault/failure condition, the discharging hot (very hot) water is replaced with incoming cold water ... which lowers the temperature of the water in the tank (which fulfills the intended and the design and reason for the T&P relief valve) ... the temperature of the water in the water heater is no longer 'hot', and instead likely only able to maintain 'warm' ... and when the occupants try to use hot water ... they will find out that something is wrong with the water heater.

I suspect that not having hot water will get action (call a plumber) quicker than water running across a floor in an out of the way location.

Thus, some codes still want the T&P discharge to go directly to the outdoors (with restrictions on the length, number of elbows, and not going uphill).

While codes based on the ICC codes want the discharge to be in the same space as the water heater is located.

I don't write the codes or make the rules - only enforce/write up the rules applicable to the location.

Just information to ponder.

[Paul Douglas]

There are two basic schools of thought on the discharge from a water heater T&Park relief valve - when a T&P relief valve discharges it may be an indication of a fault with the water heater (excluding a leaking T&P relief valve). That indicated failure is the water heater failing to stop heating - which can create a boiler bomb being made.

Both schools of thought are based on the fact that the occupants need to know that something is wrong with the water heater - the method of letting the occupants know is different.

- One school of thought is to install the water heater in the middle of the dining room and any discharge from the T&P will be seen ... but water heaters are not installed in the middle of dining rooms are they ... water heaters are installed in out of the way locations (this is not factored into this school of thought's reasoning) ... which ends up with the discharge being in that same out of the way location. Seems counterproductive and counterintuitive - but most codes are written that way.

- Another school of thought is to discharge the T&P discharge directly to the outdoors (most, if not all, codes used to be this way). With the T&P discharging under the described fault/failure condition, the discharging hot (very hot) water is replaced with incoming cold water ... which lowers the temperature of the water in the tank (which fulfills the intended and the design and reason for the T&P relief valve) ... the temperature of the water in the water heater is no longer 'hot', and instead likely only able to maintain 'warm' ... and when the occupants try to use hot water ... they will find out that something is wrong with the water heater.

I suspect that not having hot water will get action (call a plumber) quicker than water running across a floor in an out of the way location.

Thus, some codes still want the T&P discharge to go directly to the outdoors (with restrictions on the length, number of elbows, and not going uphill).

While codes based on the ICC codes want the discharge to be in the same space as the water heater is located.

I don't write the codes or make the rules - only enforce/write up the rules applicable to the location.

Just information to ponder.

Great explanation of the 2 school of thoughts and how the code is not always right. Sometimes you have to make your best judgement. Safety wise I like the 2nd school of thought. A request for a variance from the ICC code would be needed.

- - - Updated - - -


There are two basic schools of thought on the discharge from a water heater T&Park relief valve - when a T&P relief valve discharges it may be an indication of a fault with the water heater (excluding a leaking T&P relief valve). That indicated failure is the water heater failing to stop heating - which can create a boiler bomb being made.

Both schools of thought are based on the fact that the occupants need to know that something is wrong with the water heater - the method of letting the occupants know is different.

- One school of thought is to install the water heater in the middle of the dining room and any discharge from the T&P will be seen ... but water heaters are not installed in the middle of dining rooms are they ... water heaters are installed in out of the way locations (this is not factored into this school of thought's reasoning) ... which ends up with the discharge being in that same out of the way location. Seems counterproductive and counterintuitive - but most codes are written that way.

- Another school of thought is to discharge the T&P discharge directly to the outdoors (most, if not all, codes used to be this way). With the T&P discharging under the described fault/failure condition, the discharging hot (very hot) water is replaced with incoming cold water ... which lowers the temperature of the water in the tank (which fulfills the intended and the design and reason for the T&P relief valve) ... the temperature of the water in the water heater is no longer 'hot', and instead likely only able to maintain 'warm' ... and when the occupants try to use hot water ... they will find out that something is wrong with the water heater.

I suspect that not having hot water will get action (call a plumber) quicker than water running across a floor in an out of the way location.

Thus, some codes still want the T&P discharge to go directly to the outdoors (with restrictions on the length, number of elbows, and not going uphill).

While codes based on the ICC codes want the discharge to be in the same space as the water heater is located.

I don't write the codes or make the rules - only enforce/write up the rules applicable to the location.

Just information to ponder.

Great explanation of the 2 school of thoughts and how the code is not always right. Sometimes you have to make your best judgement. Safety wise I like the 2nd school of thought. A request for a variance from the ICC code would be needed if it did not allow discharge to the outdoors. The 2006 IRC P2308.6.1 Requirements for discharge pipe has been updated from the previous 2003 and appears to allow outdoor discharge. Note 5. Discharge to the floor, to an indirect waste receptor or to the outdoors. Where discharging to the outdoors in areas subject to freezing, discharge piping shall be first piped to an indirect waste receptor through an air gap located in a conditioned area.

[John Kogel]

Set the tank in a drain pan with a drain to the outdoors. TPR into the pan, pan to outside, satisfies all the requirements, and is better.
Usually electric tanks here will spring a leak long before the TPRV ever leaks a drop.

[Jerry Peck]

Set the tank in a drain pan with a drain to the outdoors. TPR into the pan, pan to outside, satisfies all the requirements, and is better.
Usually electric tanks here will spring a leak long before the TPRV ever leaks a drop.

Drain pan drain piping is typically CPV? Right?

CPV is not rated for hot water, the drain pan drain piping needs to be CPVC or other material approved for use as water distribution pipe ... per the code.

You have also now created a problem ... the water heater is not intended to be set in water, and when the T&P relief valve discharges into the drain pan, about 1/2"-3/4" of water remains in the drain pan - that does not satisfy any requirement. :pop2: