Expansion Tank for Water Heater

[AverageHomeowner]

I had my water heater replaced five years ago in my condo. It's a 30-gallon gas unit and it has been working well. When put in, the installer recommended I add a thermal expansion tank (TET) because my water supply is on a closed system. At that time, as a layperson, I did not understand the reasons given for a TET so I simply declined because of the additional cost.

Since then, I have learned a few things about plumbing and I now appreciate the value of a TET. While I have not had any problems with my water heater, I am a firm believer in preventive investments. So I plan to hire a plumber to install a TET. I want to be an informed customer this time around so I researched the installation process for a TET and I have several questions I am seeking your guidance on as this is more complex than I would have thought.

First, some background on the location of my water heater. Most of the illustrative photos I’ve seen on various web sites show a water heater in a spacious basement with a protruding rigid pipe that lends itself to easy installation of the TET. Jeez, with some luck I could probably do it myself in those circumstances! However, my situation is the other extreme. My water heater is cramped in a small hallway closet next to my hot air furnace (see photo). It is connected to the water supply by copper flex pipe, not rigid pipe, as I am in California and subject to the CA Plumbing Code which considers earthquake movement.

Here we go, one topic at a time:

1) Tank Support – I only need a small TET for my 30-gallon water heater. A two-gallon unit like the Watts DET-5 sold at Home Depot for less than $40 should work fine. Watts seems to be a reputable brand. I understand the TET should be supported by brackets or hangers to hold its weight. Empty, the tank is only 7 pounds. But filled with water, it could weigh up to 23 pounds. My first impulse was to rely on the “universal expansion tank bracket” that MUST be available in every well stocked hardware store. Surely, some entrepreneurial plumber got rich inventing one of those! However, I discovered there is no such thing and every job appears to be a custom build. So for my case, I propose to attach a wood block to the wall above the water heater. This can be a 2x4 run horizontally across the wall and attached to wall studs with nails. Then position the TET horizontally against the wall, just below and parallel to the wood block, and fasten the TET to the wood block using two straps (plumbers tape) attached to the wood block using wood screws. This configuration should anchor the TET against the wall in the very limited space I have in this closet. Alternatively, I could try to use standard shelf brackets to support the TET, but I’m not sure this would be as secure. Question: Does strapping the TET to the wood block using plumbers tape sound like a good approach?

2) Pipe Connection – As I indicated, I have flex copper pipe (see photo). I plan to have the TET installed on the cold water side between the water heater and the gate-type shutoff valve (the valve is shown in my photo with a blue knob). However, I don’t know where the 3-way T-Connector should be positioned. I don’t know if you can split a flex pipe for a T-Connector, as I’ve only seen T-Connectors on rigid pipe. My intuition tells me that fewer connections make a more reliable pipe network, so there must be some best practice. Questions: Should the T-Connector be attached directly on the water heater, or directly on the TET, or directly on the cold water shutoff valve, or where? Also, does the CA Plumbing Code require flex copper pipe between ALL connections, or just from the water heater to the next adjacent component/connector, where it can be rigid pipe from there on?

3) Isolation Valve – This may be an optional item. I read on DIY plumbing forum a recommendation to install a ball-type valve just before the TET to enable convenient shutoff if the TET requires service. Asking for opinions on this because it sounds like adding another valve is overkill. Questions: Does the TET require regular servicing? Or, is there significant value in having this isolation valve in the rare event the TET needs to be serviced or replaced? Wouldn’t the cold water shutoff valve for the water heater be sufficient?

4) TET Replacement: This is good to know for the future. Question: Should the TET be replaced with a new unit at the same time the water heater is replaced?

Thanks in advance for your answers which I hope will help others with similar questions. By researching this project, I have a much greater appreciation for all the factors that need to be considered to get this job done right. I hope the plumber I hire feels the same way.

[PLUMBER RICK]

i think you're over analyzing the whole expansion tank thing.

first off, rheem does not make a 35 gallon gas water heater

secondly you live in a condo. i'm assuming you don't have your own water meter serving just your unit so realistically, you're providing thermal expansion protection for the entire building.

have you ever connected a pressure gage to your system and checked the pressure with the heater running and sitting idle? what were the highs and lows?

is there a check valve or back flow preventer installed on your water service?

unless you know these answers, then a 2 gallon expansion tank might not be sufficient. then again, unless you actually know the pressure curve in your building, an expansion tank might not even be necessary.

please post a picture of the name plate with the 35 gallon capacity clearly shown. i need to see what i've never ever seen

i need information technology too

rick.

[NHMaster3015]

Under the IPC, expansion tanks are required for all water heaters regardless of pressure.

[breid1903]

i don't know cal code. but go back to watts.com. look at instructions. you can put tank on the cold water line anyplace past house shut off + back flow preventer + pressure regulator. where ever you want. we have a well. our well troll is on a self with straps like you mentioned. it's a lot bigger than yours. works fine. i've put them in closets, under counters, in garages and in non freezing attics. have fun. breid

[EasyEman]

Don't store all you cleaning supplies and tools etc in you water heater closet. The heater needs air to burn all that stuff just makes it harder to draw air.

[AverageHomeowner]

You are correct ... it is only a 30-gallon water water (not 35). I revised my post. Thanks for this callout.

My condo unit has its own water meter. Just outside my building, there is a PRV valve (Watts 25AUB) and on the street there is a backflow valve. The PRV valve was recently replaced and my water pressure is now in the normal range (approx 60 PSI). Previous to the PRV replacement, it was over 100 PSI which was a tipoff that the PRV valve was faulty.

As the other gentleman indicated, the CA Plumbing Code section 608.3 requires an expansion tank for all closed systems.

Still anxious to hear anyone's recommendation on where the T-Connector goes?

[EasyEman]

Maybe out side at the service. You'd have to run the 3/4 from the valve out to an area where there is space then loop back to the heater otherwise.

[PLUMBER RICK]

Originally Posted by AverageHomeowner

You are correct ... it is only a 30-gallon water water (not 35). I revised my post. Thanks for this callout.

My condo unit has its own water meter. Just outside my building, there is a PRV valve (Watts 25AUB) and on the street there is a backflow valve. The PRV valve was recently replaced and my water pressure is now in the normal range (approx 60 PSI). Previous to the PRV replacement, it was over 100 PSI which was a tipoff that the PRV valve was faulty.

As the other gentleman indicated, the CA Plumbing Code section 608.3 requires an expansion tank for all closed systems.

Still anxious to hear anyone's recommendation on where the T-Connector goes?

you can install it anywhere in the cold water system.

but if i'm understanding this correctly, you have your own water meter for your own unit serving just you.

but there is also a backflow preventer serving the entire complex.

if this is true, then you will be protecting the entire complex with your expansion tank unless your meter has a double check valve incorporated into it.

how many units are in your complex?

how many water meters?

how many back flow preventers?

sure an expansion tank is required for a closed system, but if i'm understanding the installation correctly, you're wasting your time with a little 2 gal. tank if your complex is on 1 backflow preventer. you would be protecting/ absorbing the pressure from every heater past the back flow preventer.

go get yourself a pressure gage and install it on a faucet at either a hose bibb or the tank drain bibb. get the gage that has a second needle that registers the maximum pressure reached. this should go up at night when there is no flow and the heater is heating.

once again this is based on my theory how your complex is piped.

rick.

[AverageHomeowner]

Originally Posted by breid1903

i don't know cal code. but go back to watts.com. look at instructions. you can put tank on the cold water line anyplace past house shut off + back flow preventer + pressure regulator. where ever you want. we have a well. our well troll is on a self with straps like you mentioned. it's a lot bigger than yours. works fine. i've put them in closets, under counters, in garages and in non freezing attics. have fun. breid

Thanks for weighing in. Unfortunately, I don't have a lot of flexibility on where to put the tank. My condo association has very strict rules about installing items around the building so that every unit has a uniform appearance. My neighbor has an expansion tank in their water heater closet, just as I am proposing.

[AverageHomeowner]

Originally Posted by PLUMBER RICK

you can install it anywhere in the cold water system.

but if i'm understanding this correctly, you have your own water meter for your own unit serving just you.

but there is also a backflow preventer serving the entire complex.

if this is true, then you will be protecting the entire complex with your expansion tank unless your meter has a double check valve incorporated into it.

how many units are in your complex?

how many water meters?

how many back flow preventers?

sure an expansion tank is required for a closed system, but if i'm understanding the installation correctly, you're wasting your time with a little 2 gal. tank if your complex is on 1 backflow preventer. you would be protecting/ absorbing the pressure from every heater past the back flow preventer.

go get yourself a pressure gage and install it on a faucet at either a hose bibb or the tank drain bibb. get the gage that has a second needle that registers the maximum pressure reached. this should go up at night when there is no flow and the heater is heating.

once again this is based on my theory how your complex is piped.

rick.

Rick, I have my own water meter and separate billing from the water dept. Here is the basic configuration from the water main (from memory).

At the street, the water main goes to my meter and then to a backflow valve. The meter and backflow valve are specific to my unit. There are four residential units in my building, and each unit has its own meter/backflow valve at the street.

At the outside of the building, each of the four units has a shutoff valve and a PRV valve. So I believe the water pressure inside my unit is well isolated to my unit only.

The sizing of the expansion tank is based on the Watts reference guide for a water heater of my size (30 gal). And as a practical matter, I could not fit a larger tank in my small water heater closet anyway.

I don't have any specific water pressure problems I am trying to address with the expansion tank. It is simply to take up any excess pressure that might result from thermal expansion of my water heater (for example, if I go away on vacation for a couple weeks). I think of it as insurance, not a repair. This is a special concern for a condo owner as my water heater sits in the interior of my unit (no basement). Any pressure-related water problems could be catastrophic to my living area. And I have shared walls with my neighbors, so I am responsible for any water damage I may cause to their units. These accidents are rare, but do happen. Let me know if you think I am being too conservative ... something Californians are not known for.