When are expansion tanks required?

[Beniah Naylor]

We have found some pressure reducing valves, primarily manufactured by Watts, that allow water to backflow through them out into the utility's water main.

Does anyone here allow this as an alternative to installing an expansion tank when a storage type water heater is installed? I am looking for standard practice of enforcement in your area. The code sections are P209.3.4 in the IRC, and 607.3 in the IPC.

Thanks!

 

[mtlogcabin]

No
P2903.4.2 requires backflow prevention or a check valve if you have water heating equipment installed
A pressure reducing valve may not be designed to prevent backflow

P2903.3.1 Maximum pressure.
The static water pressure shall be not greater than 80 psi (551 kPa). Where the main pressure exceeds 80 psi (551 kPa), an approved pressure-reducing valve conforming to ASSE 1003 or CSA B356 shall be installed on the domestic water branch main or riser at the connection to the water service pipe.

Performance Requirements for Water Pressure Reducing Valves for Potable Water Distribution Systems​

Organization:	ASSE
Publication Date:	1 December 2020
Status:	Active
Page Count:	20

Scope:​

Description
Devices covered by this standard are self-contained, direct acting, single diaphragm types. Devices shall be permitted to have an integral strainer, separate strainer connected to the valve inlet, or be without strainer. Devices shall be permitted to be with or without an integral by-pass relief valve.


P2903.4.1 Pressure-reducing valve.
For water service system sizes up to and including 2 inches (51 mm), a device for controlling pressure shall be installed where, because of thermal expansion, the pressure on the downstream side of a pressure-reducing valve exceeds the pressure-reducing valve setting.

P2903.4.2 Backflow prevention device or check valve.
Where a backflow prevention device, check valve or other device is installed on a water supply system using storage water heating equipment such that thermal expansion causes an increase in pressure, a device for controlling pressure shall be installed.

 

[mtlogcabin]

Our Public Works provides the double check backflow preventer on the water meter. The double check thus requires an expansion tank be installed.
Do your customers where you have discovered these have a higher water consumption than others? We found the issue you are describing resulted in the older water meters "rocking" which resulted in billing for more water than actually went through the meter

 

[Msradell]

Our Public Works provides the double check backflow preventer on the water meter. The double check thus requires an expansion tank be installed.

Just having the double check doesn't necessarily mandate having an expansion tank. Some areas do not require them even if you have a double check, would probably want one but they are not a code requirement.

 

[ICE]

Our code allows a pressure regulator in lieu of an expansion tank as long as the regulator setting is a maximum 100psi. There is one plumbing contractor that upsells an expansion tank with every water heater that they install. The company is from Washington state and they contract with big box stores. Water heaters is all that they do. They are pricey and then insist that the code requires an expansion tank. I have had customers ask about the code requirement for the expansion tank. I advise them to tell the contractor to remove the expansion tank.

Whats worse is that the company will not install anything that was not existing without charging more. For example, if the T&P valve was not plumbed to an approved location the contractor waits until a correction is written and then hits the customer with a fee. I have returned for the followup inspection and the customer begs me to not write any more corrections because they can't afford it.

Commercial properties have check valves and they get an expansion tank. I have encountered residential installations that have a long water pipe in a hot attic....they got an expansion tank also. You have to play it by ear.

 

[Beniah Naylor]

ICE - can you provide a picture of the pressure regulator you are talking about? What alternative "devices to control pressure" exist for thermal expansion?

mtlogcabin - Our city water service does not install a backflow device of any kind at the meter for IRC houses, except in special cases. I have not heard about anyone noticing that they are getting billed for more water than they use but it certainly could be happening. I agree that if they did install a check valve at the water meter that it would automatically kick in the requirement for a thermal expansion control device. The commentary in the IPC for this is over 3 pages long, and mentions that scenario specifically.

 

[SCBO1]

Our Public Works provides the double check backflow preventer on the water meter. The double check thus requires an expansion tank be installed.

Commercial properties have check valves and they get an expansion tank.

Same here, required expansion tank when they pull a new waterheater permit. We have a closed system with checks and doubles.

 

[fatboy]

No individual backflow devices at IRC structures, so no expansion tank required.

Our new construction does require a PRV be installed, to get the pressure down to 80 psi.

 

[mtlogcabin]

IRC no requirement for expansion tanks that I could find

We use the UPC

UPC 608.2 and 608.3 require expansion tanks


2018 IPC
607.3 Thermal expansion control.
Where a storage water heater is supplied with cold water that passes through a check valve, pressure reducing valve or backflow preventer, a thermal expansion control device shall be connected to the water heater cold water supply pipe at a point that is downstream of all check valves, pressure reducing valves and backflow preventers. Thermal expansion tanks shall be sized in accordance with the tank manufacturer’s instructions and shall be sized such that the pressure in the water distribution system shall not exceed that required by Section 604.8.

 

[Beniah Naylor]

IRC no requirement for expansion tanks that I could find

P2903.4.1 Pressure-reducing valve.
For water service system sizes up to and including 2 inches (51 mm), a device for controlling pressure shall be installed where, because of thermal expansion, the pressure on the downstream side of a pressure-reducing valve exceeds the pressure-reducing valve setting.

P2903.4.2 Backflow prevention device or check valve.
Where a backflow prevention device, check valve or other device is installed on a water supply system using storage water heating equipment such that thermal expansion causes an increase in pressure, a device for controlling pressure shall be installed.

I guess I was too specific when I said "expansion tanks" - I meant any device that can deal with the thermal expansion. Expansion tanks are just all anyone uses for that around here.

 

[Beniah Naylor]

So, my understanding of what you all are saying is that:

In commercial, (IPC) world, you will be installing an expansion tank if you have a pressure reducing valve or a check valve on the water meter.

In a residential (IRC) setting, you will be installing a "device for controlling pressure" - not necessarily an expansion tank, but could be, if you have a pressure reducing valve or a check/backflow valve at the water meter.

So my question is, if you have an IRC home, and you have a pressure reducing valve with an integral by-pass relief valve, and no check valve on the water meter, then would you require an additional "device for controlling pressure" or not? Is my summary above correct?

 

[ICE]

Is my summary above correct?

In California the pressure regulator can serve as the expansion control device if the system is designed by a plumbing professional (any plumber) and the maximum high setting of the regulator is 100psi or less. Seldom does a residential plumbing system experience too much water pressure because of a water heater. In fact, seldom is there an expansion tank installed on a residential plumbing system and I have never been made aware of a need for one with the exception of apartment buildings.

Apartment buildings can have long lengths of water pipe in an attic which can get hot enough to require an expansion tank. Now having said that, I must qualify the statement in that I caused a few apartment buildings to install an expansion tank without proof of expansion. So I could be full of BS on that.

Most commercial facilities have a double check valve. That restricts the pressure to the system and a pressure regulator will not suffice as the expansion control measure.

 

[Ed Cooke]

We have found some pressure reducing valves, primarily manufactured by Watts, that allow water to backflow through them out into the utility's water main.

Does anyone here allow this as an alternative to installing an expansion tank when a storage type water heater is installed? I am looking for standard practice of enforcement in your area. The code sections are P209.3.4 in the IRC, and 607.3 in the IPC.

Thanks!

In Iapmo code land, the decision needs to be identified as to why is there a regulator. If your system is not over 80psi, then no requirement. If it is, check 608.2 or 608.3. There are several methods of compliance, and of course an engineer can provided alternative designs as long as they meet standard engineering practices.
Please read carefully to understand those possibilities.