Ask an INGO plumber - water heater edition

[JettaKnight]

Please explain to me when you install that bladder tank, how it will reduce the water pressure in the system?

It won't, it just becomes part of the system and is subjected to the same pressure.
Pressure is created by resistants to flow, and head pressure.

Au contraire!

PV/T = PV/T


Take a long, hot shower, turn off all the water. The system is sealed now (i.e. no flow). There can be no change in volume. There is no resistance. Equilibrium has been achieve. The check valve (if you have one) will allow the pressure in your pipes to increase (i.e. more water comes in from the street), but not decrease (you can't push any water back out).
As the water heater works, it's heating up that water - temperature increases, but the volume is fixed, so the pressure must increase.


With an expansion tank, the temperature will climb, the pressure will increase some, but tank will expand, and increase the volume in system.



So, it does reduce the impact of pressure increase due to water heating, but enough to need it? I dunno, I can only explain the theory.

 

[Jaybird1980]

There is some thermal expansion occurring, but the pressure in that tank is equal to the tank of heater.
The question was how does it reduce pressure.
It does have some shock absorbtion properties that could be beneficial.

 

[Clay Pigeon]

Au contraire!

PV/T = PV/T


Take a long, hot shower, turn off all the water. The system is sealed now (i.e. no flow). There can be no change in volume. There is no resistance. Equilibrium has been achieve. The check valve (if you have one) will allow the pressure in your pipes to increase (i.e. more water comes in from the street), but not decrease (you can't push any water back out).
As the water heater works, it's heating up that water - temperature increases, but the volume is fixed, so the pressure must increase.


With an expansion tank, the temperature will climb, the pressure will increase some, but tank will expand, and increase the volume in system.



So, it does reduce the impact of pressure increase due to water heating, but enough to need it? I dunno, I can only explain the theory.

I understand quite well. I did that journeymanship thing. The bladder tank is not only for thermal expansion its there to soften the impacts on the water lines when opening and shutting off the water fixtures. It reduces the hammering impact on the waterlines fittings.

I posted asking Indybeerman how an expansion tank lowers the pressure when one is installed...

 

[DoggyDaddy]

I understand quite well. I did that journeymanship thing. The bladder tank is not only for thermal expansion its there to soften the impacts on the water lines when opening and shutting off the water fixtures. It reduces the hammering impact on the waterlines fittings.

I posted asking Indybeerman how an expansion tank lowers the pressure when one is installed...

Oh man, I remember Dad yelling at me for shutting off the bathtub faucets too quickly after taking a shower when it would cause a "bang" in the pipes. I'm living in my childhood home now and I'm still conscious of doing that.

 

[Clay Pigeon]

Oh man, I remember Dad yelling at me for shutting off the bathtub faucets too quickly after taking a shower when it would cause a "bang" in the pipes. I'm living in my childhood home now and I'm still conscious of doing that.

Yep.. When water pressure in a home system closes in on 70psi and lower pressures in the smaller pipe that tends to be used now days so folks get hot water to fixtures farther away from the water heater faster depending on how the pipes were run you can get hammering.
When water is pushed faster than say 18 fps or faster you tend to start to have problems.
Like hammering, toilets that sound like turbines when filling and shortened pipe and fixture life.

 

[Jaybird1980]

I understand quite well. I did that journeymanship thing. The bladder tank is not only for thermal expansion its there to soften the impacts on the water lines when opening and shutting off the water fixtures. It reduces the hammering impact on the waterlines fittings.

I posted asking Indybeerman how an expansion tank lowers the pressure when one is installed...

So you do get it, I thought you had an actual question.
Shouldn't of got involved.

 

[Clay Pigeon]

So you do get it, I thought you had an actual question.
Shouldn't of got involved.

LOL.... No worries here my friend..

 

[Bowman78]

Replace the water heater, it’s living on borrowed time. I had a 14-15 yo WH that had a slightly leaky tp valve, I’m talking a occasional dribble. Basement location with a floor drain. You are gambling with a unit that old, replace it and sleep well. I compare it to old tires or brakes on a car, they will fail at the worst possible times!

 

[JettaKnight]

I understand quite well. I did that journeymanship thing. The bladder tank is not only for thermal expansion its there to soften the impacts on the water lines when opening and shutting off the water fixtures. It reduces the hammering impact on the waterlines fittings.

I posted asking Indybeerman how an expansion tank lowers the pressure when one is installed...

These are just example numbers, but let's say without an expansion tank the pressure goes from 70 psi to 75 psi. With the tank it would go from 70 psi to 73 psi.


Example numbers, but shows the physics behind it, IANAP.

 

[churchmouse]

These are just example numbers, but let's say without an expansion tank the pressure goes from 70 psi to 75 psi. With the tank it would go from 70 psi to 73 psi.


Example numbers, but shows the physics behind it, IANAP.

The overall pressures remain exactly the same. The tank absorbs shock and "EXPANSION hence the name "EXPANSION" tank.
If you are on a municipal water supply you will experience what ever they are delivering to you pressure/volume wise. There is no way past this outside of a supply side regulator.

Now, on a well delivery system yes when the pump is shut of by the pressure switch and the foot valve engages you "Might" see a slight drop with the tank.

Ask me how I know.....

 

[Clay Pigeon]

These are just example numbers, but let's say without an expansion tank the pressure goes from 70 psi to 75 psi. With the tank it would go from 70 psi to 73 psi.


Example numbers, but shows the physics behind it, IANAP.

And again Jetta, the question I asked Indybeerman was to explain how the pressure dropped when a bladder tank was installed.

 

[JettaKnight]

And again Jetta, the question I asked Indybeerman was to explain how the pressure dropped when a bladder tank was installed.

OK, I went back and re-read, and I think I now know where we're all tangled up.

Indybeerman either misspoke, or is mistaken.


An expansion tank doesn't reduce the pressure, it can reduce the increase in pressure.