Thermal expansion

[micky]

Talking about plumbing with my friend, found out she has an expansion tank on her water system, but since she uses a well, what is the point?

Are they afraid she'll contaminate the well, the aquifer that neighbors use?

I don't understand backflow at all. Assuming I, using city water, had thermal expansion, no backflow preventer, and backflow, how much can the water possibly expand? How far back can it flow? 3 or 4 inches? Water, even the water in a hot water tank, can't expand that much. 3 or 4 feet? Surely not far enough to meet the water that's going to my neighbor's house.

Yet they have laws about this. To think the laws have no point would mean stupid people are promoting the laws. Or maybe it's the powerful backflow preventer lobby. Is the government dominated by Big Flow?

[Skid Marks]

It's an election year. Biden will lock down your water supply. The expansion tank prevents the bird flu in your cow milk from contaminating the eggs and icemaker in your refrigerator and the mail-in ballot on the kitchen table. Maybe you should prolly follow the science and wear an N-zero mask and get an modRNA bird flu vaxxxcine? You should also social distance your eggs and ice cubes at least 6 feet apart.

[Retirednoguilt]

There more than just back-flow that an expansion tank prevents. See:

[Ed P]

Many places now require back flow prevention. Slim odds it can happen, but if the city water loses pressure, your residential boiler, that may have chemicals, can push back in the system and potentially contaminate. Irrigation systems can bring in chemicals too.

When we ran boilers at work from city supply, it was 150 psi and could potentially travel some distance and of course, we used chemicals.

My water supply to the kitchen passes through the attic. It gets warm up there in Florida and the first thing in the morning, the pressure is increased.

My present house has a preventor but I did survive over 70 years without one.

[Clare Snyder]

When you use a well pump you NEED an "expansion tank" - it is actually called an accumulator and it stores water under pressure (pressure provided by air compressed in the top of the tank) so the pump doesn't have to stop and start every time you crack the tap open and so pressure remains relatively constant - liquids are non-c0mpressible so pressure would be whatever the pump can produce - instantaniously. This kind of pump is often used in RVs - on-demand pumps - with relatively low max pressure regulated by a pypass. Anti backflow valves and anti aiphon valves DO prevent contaminated water frfom being "sucked" back into the supply system / well - particularly in the event supply pressure drops or dissapears. Put your hose into your pool and turn it on, then have a pressure failure that allows water to flow back to the pump/supply and it starts a siphon and sucks all ypour pool water into the supply. Replace pool with a water puddle - same thing. Those devices (and rules) ARE there for good reason. It's not (just) (or at all) the "democrats" trying to control you!!!!!!!

[Clare Snyder]

a 40 gallon water tank contents will expand by roughly 1.25 gallons (roughly 3%) when heated from ground temperature (roughly 45F ) to

150F. Without a compressible expansion chamber that would produce INCREDIBLE hydraulic pressure within the tank and pipes if restrained by an anti-backflow valve - seriously damaging the system.

[micky]

I have no boiler, only an electric water heater. Except for some heat, everything in it came from the water company to begin with.

I'v e been reading and the pressure regulators advertised seem to all have bypass valves, so I suppose the one I had that just failed did also, and so will the new one. That would relieve pressure if the water heater were overheating, and so would the TP valve on the water heater. That's its purpose. However one page hinted that the water meter might prevent backflow. Mine is undergound and no one has looked at it 49 years since it was installed (becasue all 100 of us share one water meter. in fact I think 5 or 600 of us share one meter.)

[micky]

Darn, I've misplaced my swimming pool.

Yes, the Democrats are trying to control us. Every new idea is from the Democrats, and they are all bad. Don't you listen to the radio. We need to go back to 1776.

[Scott Lurndal]

It's because there is a check valve on the pump. The expansion tank (which is associated with the hot water heater), prevents the internal piping from potentially bursting due to a pressure increase in the hot water heater.

[Scott Lurndal]

Thats the pressure tank, often used with a booster pump when the well pump fills a water tank. I have two, one for the irrigation well and one for the potable supply tank.

The expansion tank is for the hot water heater to prevent burst pipes when there is a check valve on the supply line (from the pump, tank or city water system). Required in many states.

[Jim Joyce]

Minor quibble, but can we not call it a hot water heater? It's just a water heater. If anything, it's a cold water heater, since the incoming water is cold. If the incoming water was already hot, there would be no work for the heater to do. :)

[Bob F]

The check valve is between the pump and the pressure tank, which functionally is an expansion tank.

[micky]

That is a great environmental idea. If the city water company would send out hot water, howeowners could save a lot of money by using little or no gas or electricity in their water heater. Plainly it's more efficient to heat it all in one place than have all these little heaters.

We also need to devise a way for more wells to deliver hot water.

[Bob F]

There is a facility in many cities piping hot water or steam to businesses downtown.

[micky]

Yes, I've beena big influence on some cities.

[Scott Lurndal]

That's pretty silly.

How much heat would be lost transporting the hot water and holding it in pipes underground? How much would it cost to build the infrastructure in existing cities?

There are communities in many parts of the world that distribute hot water (steam) for heating, but that infrastructure was built with the community (or installed a century ago). Even parts of Manhatten still get steam from a central source for heating.

[Bob F]

[rbowman]

[rbowman]