Expansion Tanks

[Anonymous]

Posted by: Jimbo (old forum transfer)
Posted - 01/25/2002 : 10:22:43

I'm not sure why expansion tanks have become necessary now, in most counties. We've had water heaters for many years, without expansion tanks, so why now?

But my real question is: can expansion tanks be located at some distance from water heater? I'd like to put a small, low boy electric WH in the corner of a lower kitchen cabinet, and am wondering if I can put exp tank in, say, attic above? Or, is there a small "relief valve" type substitute for exp tank?

[Anonymous]

Posted by: Wgoodrich
Posted - 01/25/2002 : 14:17:38

Jimbo there is a lot of info not being said in you post, such as if this is a residential single family dwelling, duplex, apartment building, commercial building and if so what use of commercial building.

If we are talking of a one and two family dwelling type structure you also must confirm which plumbing code we are going by. Is the Code active in your area the CABO one and two family, The Uniform plumbing Code Boca. All the above would have an affect to the proper answer to your question.

If you are talking of a one or two family dwelling and if the CABO one and two is approved as code in your area then a thermal expansion tank is only necessary if youf building supply pressure is greater than the required relief valve pressure setting. or when any device is installed that prevents pressure relief. If a thermal expansion tank is required you are also required to install a pressure relief valve.

If you have a water heater valve that is approved for use as both a pressure relief and a temperature relief valve then the CABO exempts the requirment of a thermal expansion tank.

There is no requirement where a thermal expansion tank or its required pressure relief valve is located as long as there is no equipment that would prevent the relief of pressure if necessary.

The pressure relief valve required to serve the thermal expansion tank is allowed to be omitted if the relief valve at the water heater is a dual pressure and temperature relief valve.

A second thought along the line of an expansion tank is as follows;

If you have a well system there is a pressure style expansion tank required to supply even pressure and to lower the cycling of the start and stop of your well pump.

The above is what is required in the CABO for one and two family dwellings. If this is an apartment building or commercial building then you must refer to the BOCA uniform plumbing Code to get your answers. Then once you know what the National Codes say you must research exactly what your local ordinances say in revisions to these national rules. Then you must talk to your AHJ to make sure he reads the rules same as you read these rules.

The CABO Code still says that if you have a combination pressure and temperature relief valve with not shut offs or bypasses to rend the relief valve useless or restricted then you are not required an expansion tank in this potable water system unless you need the pressure tank to serve the water pump to maintain constant pressure and to lesson the cycling on and off of the water pump.

Hope this is of some help

Wg

[Anonymous]

Posted by: Jimbo
Posted - 01/25/2002 : 16:11:12

Wg,

Guess I went off half ****ed. This will be a single family home, to be built in Curry County, OR, this summer. I was talking to a friend about what I wanted to do (putting elec. WH under kitchen cabinet), and he asked about expansion tank, saying: "They ALL require them now!"

Truth is, I don't know for sure about Curry County. I'll be using county water, piped in, and I think I want to use 2 WHs, one for domestic and one for hydronic floor heat. The literature I've got for the (Kenmore) WH does not give info about relief valve, which I'll have to check on.

But, whatever, and I'll have to talk to building inspector up there, MOST LIKELY I will be able to use correct pressure/temp relief valve?

BTW, electric is so cheap up there (.05 KWH, compared w/ $1.65+ for propane) that it's much cheaper to heat w/ electric.

[Anonymous]

Posted by: Wgoodrich
Posted - 01/25/2002 : 19:23:23

Jimbo most likely you won't have to install an expansion tank unless you have some local ordinance pertaining to locality rules if you are being served by Utility water and as long as you provide the pressure/temperature relief valve propely. The AHJ has the final ruling on the subject so be sure to make contact with him before you get committed in design.

Also you might want to research into the on demand tankless water heaters. They take a large service and branch circuit ampacity rating, but only uses electricity as you use water. No maintaining temperature of the storage tank of your hot water heater. Seems like this it the technology that new water heating is going to. Might be worth your reading up on the subject looking for some stats on the subject of tankless on demand hot water heaters. This on demand hot water heaters also eliminate the need of heat loss and electrical cost due to a hot water circulator and having to run the hot water a while before you far away faucets finally get hot. It is instant hot water.

Glad your electric is so inexpensive up or over there. Might be because of all the windmill generated outputs that were installed on the coast in the State of Washington. Problem is that I built a 3600 square foot new home in 1980. At that time electric around here was the most economical of all fuel sources. Then as time went by natural gas beat electric, then Lp beat natural gas, the fuel oil beat natural gas, then electric beat natural gas just depending on the year during the 22 years that I have had this home. Kind of makes you want to install a geo thermal heat pump with an electric and a gas and a fuel oil back up heating source. If the price of a certain fuel changes with the wind in value you could jump back and forth between back up heating systems. That geo thermal stealing heat from the earth seems to be the only constant allowing you to start your heating source at a constant 55 degrees. Boy is mother nature gererous or not?

Just thought that I would spur some thought for you.

Hope this helps

Wg

[Anonymous]

Posted by: Jimbo
Posted 01/26/2002 : 08:57:32

Wg, I've looked into tankless a bit, but there don't seem to be many electric models, and their initial cost is so much more than standard tank-types, the payback might be long coming. My reasoning, also, is that since it's virtually ALWAYS coolish on the Northwest coast, the heat loss from tans will actually be helpful.

Not sure how a tankless would eliminate circulators. This will be a tiny (500SF) retirement cabin; bath and kitchen back to back w/ no fixture (except washer) more than 10' from WH.

I hear you on changing fuel costs. Actually, at this point, fuel oil would be cheapest source for BTUs, but those WHs are REALLY expensive. All in all (I think), since the place will be so small, and so well insulated, the ease and convenience of electric makes it the best choice. According to local coop, most of the power comes from hydro, with some gas. Electric price has been stable for quite a while, whereas propane has fluctuated a lot, going as high as $2.25 last year. No natural gas, since the area is remote and somewhat unpopulated.

If electric price goes up significantly, who knows, maybe I'll look into windmills!