# Here is a head scratcher



## Morning Wood (Jan 12, 2008)

A good friend of mine texted me and asked what could be happening with his shower pressure. He said when he flushes the toilet the shower pressure goes up. Yes, up. Both hot and cold go up not just cold. He replaced the cartridge in the shower. It is a symmons. He also has a oil boiler with a coil in it for hot water. I didn't have a clue and thought I might check with the WWW. Nick.


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## GettingBy (Aug 19, 2010)

Morning Wood said:


> He said when he flushes the toilet the shower pressure goes up. Yes, up. Both hot and cold go up not just cold.


A booster pump or pressure tank upstream of the WH that is overcompensating for a pressure drop?


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## madmax718 (Dec 7, 2012)

just the shower and nowhere else in the house?

Turn off the water main, purge the lines, and fill up again. Sounds like there may be an air bubble that slows the water flow to the shower, but when the toilet is filling, it causes the bubble to move, thereby allowing more water to pass by.


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## GettingBy (Aug 19, 2010)

madmax718 said:


> just the shower and nowhere else in the house?
> 
> Turn off the water main, purge the lines, and fill up again. Sounds like there may be an air bubble that slows the water flow to the shower, but when the toilet is filling, it causes the bubble to move, thereby allowing more water to pass by.


How do you get such a bubble? A firetruck up the street making a suction in the mains?


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## Texas Wax (Jan 16, 2012)

bad/hair trigger pressure regulator


Suction from a fire engine :laughing: that'd be a butt load of water (gpm) and total failure of procedure. 5-7 psi on steamer intake is as low as you supposed go. Bad chit starts to happen below that. Air is the least of it


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## GettingBy (Aug 19, 2010)

Yet a bunch of WHs were ruined by having the water sucked out of them. Maybe it was the water company that screwed up.


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## Morning Wood (Jan 12, 2008)

When you say purge the lines, you mean drain them, or blow them out with compressed air?


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## griz (Nov 26, 2009)

is he on a well?


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## Dave in Pa (Oct 10, 2009)

griz said:


> is he on a well?


Deep or shallow? Might make a difference! Jet pump or submersible, or a old sucker rod? BUT a good point!


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## tjbnwi (Feb 24, 2009)

Well tank diaphragm has gone bad or the tank pressure is set wrong. Pump cycles on when the toilet is flushed causing the pressure to go up. I bet the problem occurs a few times during a 5 minute shower, they don't notice it. 

Tom


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## griz (Nov 26, 2009)

tjbnwi said:


> Well tank diaphragm has gone bad or the tank pressure is set wrong. Pump cycles on when the toilet is flushed causing the pressure to go up. I bet the problem occurs a few times during a 5 minute shower, they don't notice it.
> 
> Tom


bingo...:thumbsup:


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## Morning Wood (Jan 12, 2008)

city water


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## griz (Nov 26, 2009)

city or your friend have a regulator on the line?


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## Morning Wood (Jan 12, 2008)

I doubt he even knows. I don't. I believe all he has is a water meter.


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## tjbnwi (Feb 24, 2009)

RPZ needs to be tested. 

http://en.wikipedia.org/wiki/Reduced_pressure_zone_device

Tom


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## CarpenterSFO (Dec 12, 2012)

It could just be the behavior of the shower valves. Some constant temperature valves act funny when the pressure changes. I don't know about Symmons.


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## Fouthgeneration (Jan 7, 2014)

Water pressures going " outside" of the mixing valve design limits?

Back flow preventer installed wrong, wore out?

foreign matter(solder in shower head) in the piping or a kinked pex line-----or hot water reheat line installed adjusted incorrectly?

Could be some type of perpetual motion(hot water) machine installed secretly by NASA:laughing:

remove the showerhead, is the aerator causing the flow to slow as pressure increases? (Damn the EPA and all their cousins)


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## GettingBy (Aug 19, 2010)

If this were an electrical circuit you can measure voltage and sometimes current anywhere along and so it is easy to troubleshoot. You can also take components out of the circuit and test them independently.
Not so with hydraulic circuits.

So, if there is a faucet that allows you access to the pressure in the lines you can put a meter on this just like you are measuring voltage, and eliminate some possibilities.



As the plumbing systems have more and more devices that regulate and limit the flow, pressure or temperature, putting some kind of tap on pipes in different places for debugging purposes sounds like not a bad idea.


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## Morning Wood (Jan 12, 2008)

Bad shower head. Fixed.


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