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Hot Water Pressure

Just installed a Buderus G115SW/5 and a LT160 indirect water tank.  Everything is working fine.  I just have crappy hot water pressure.  At first I thought it was sedment cause it is an old house.  No such luck.  Cleaning the traps helped but no enough.    I thought maybe my sub par mixing valve was the issue.  Changed that to a honeywell AM-100 also helped (might be in my head) but not enough. 

Keep in mind the water pressure before wasn't pheonomenal but I didn't have to turn my symmons shower mixer all the way around to get hot shower water.  Maybe a 1/4 turn.  Even changed the internals on the shower mixer, thinking the valve body was clogged........

It is 1/2'" piping from the boiler to the faucets and the auto fill valve is set to 22psi. 

Any help would be appreciated.

Forgot to memtion low water pressure at all faucets.


  • Larry WeingartenLarry Weingarten Member Posts: 1,173
    Starting at the beginning

    What's the cold water pressure?  From there, put your gauge on the drain of the tank and measure static pressure.  It should pretty much match the cold pressure.  Now run hot water.  Does the pressure at the tank fall off significantly?  How about if you open multiple taps?  This will help identify where the restriction is or isn't.  From there it's following on down the hot lines to find out where the pressure drops off.  Do let us know what you find.

    Yours,  Larry
  • preguntapregunta Member Posts: 4
    thank you for the quick response

    Cold water pressure before or after the auto fill?  Auto fill is set to approxiamtely 20psi.    I am not using an external guage but the guage on the boiler feed reads 20 psi also.

    I turned on the tub, kitchen sink, and bathroom sink then went donwstairs to check the pressure at the tank.  It dropped no more than 3psi   

    I hope it's not much further down in the lines.  They go into a dirt floor, 1.5' tall crawl space.
  • chapchap70chapchap70 Member Posts: 130
    Indirect Pressure, not boiler pressure.

    The 20 PSI you were referencing is boiler system pressure, and has nothing to do with water pressure at your faucets.  I believe Larry was telling you to put a gauge on the indirect drain (bottom of tank maybe) and work from there.  Normal house pressure for cold domestic water should be between 60 to 80 psi but usually closer to 60.
  • preguntapregunta Member Posts: 4
    I'm really embarrased

    The reason why I kept saying 20psi because The whole system was at 20psi.  I tee'd off of the boiler fill post auto fill value for the water tank fill.  Thusly I am getting 20psi into the water tank.  Thank you guys for helping me find my f*&k up. 

    I'll be running another T pre auto fill tonight.  I'll let you know how it goes.
  • GordanGordan Member Posts: 891

    Was this a late-night job? :-)

    Be sure to use piping that's appropriate for the expected amount of flow and pressure drop. I only say this because boiler feeds are typically (though not necessarily) 1/2" and that will definitely be insufficient.
  • preguntapregunta Member Posts: 4
    Yup....Late and sleepless

    My boiler had popped and needed to be replaced.  After getting them in the bulkhead and moving them into place It started to get cold.  I was low on sleep and expectaions were high.  Once I got it ready to fire and create heat it got warm again......  Ain't that how it works. 

    In any case I tee-d last night put in a backflow preventer, expansion tank, gauge, and ball-valve.  It goes fron 1/2" to 3/4" into the HW tank.   The hot water pressure is Excellent.  I would go as far as saying it is better that the previous boiler.  I'm sure there were restrictions in the hot water coil.   

    2 quick Questions

    question 1......I have a static pressure from the street of 50psi.  Is a PRV needed?  The only reason I could see it being necessary is as a fail safe but code could be a different case. 

    question 2....What kind of psi change are you seeing after thermal expansion?  I know this number varies from one case to another.  Just looking for "budgetary" numbers.  So I don't freak out.  (42 gallon HWT, 50psi static, Backflow Preventer)
  • Larry WeingartenLarry Weingarten Member Posts: 1,173
    50 psi...

    ... doesn't call for a pressure reducer.  Put a gauge on the tank drain valve and let the tank heat from cold.  If you get up to 80 psi or more, it's time for an expansion tank on the cold side.

    Yours,  Larry
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