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Dirty Steam Water in Hot water tank

nycpanycpa Member Posts: 108
Today I had a friend over to clean my glass gauge  of my steam boiler. 

When we drained the boiler the water was pretty dirty.  I have a low

water cutoff.  It refills after ten minutes, instead of waiting ten

minutes we added by by turning on the by pass valve.  After he left, I

decided to clean out the water in my hot water tank, A O Smith that is

four years old.  Usually, it would be only a little dirty, after half a

gallon it would run clean.  This time, the water was as dirty as my

steam boiler, never seen it like this before.  I connected a garden hose

to the drain and let it drain for twenty minutes.   It went from dark

brown to light clear.  I also let my hot water faucet run for 10

minutes.  It had a little dirty water.  I shut off the hot water flow to

my steam boiler for now.  My question is:

How could this happen,

is it possible that the hot water heater sucked water from my boiler? 

Negative pressure?  Is there a way to prevent this?  This is the first

time I've seen this.  I added a picture of my system. 

I appreciate the advice. 


  • TimcoTimco Member Posts: 2,826
    Cross contamination

    High pressure leaks into low pressure side. If you flushed or refilled a hot steamer you can cause a leak in the boier, but not cross contamination. First sign of coil leak is press relief valve on boiler trips. Tank rotting? Sat for a while?
    Working on steam and hot-water systems isn't rocket's actually much harder.
  • RJRJ Member Posts: 484
    dirty water

    Do you have a backflow preventer on the boiler.  have you had water line repairs in the area
  • nicholas bonham-carternicholas bonham-carter Member Posts: 6,540
    edited September 2013
    Dirty hot water

    If this is a home which is rarely used, and has some iron piping, then the first draws of hot water after a long period of inactivity will be brown from rust

    Also do a search here for the procedure for cleaning of the gauge glass.--NBC
  • nycpanycpa Member Posts: 108
    Steam Water in Hot wter Tank

    Thanks for the tips guys, Does the automatic water feed have a backflow prevent er in it?  If not, then I don't have a back flow preventer.  To install one, I guess I would install on the line before it goes into the auto feeder?  With a shut off valve right before it. 

    I do remember them doing water work on the main line in my street last month, but if I had dirty water in the tank because of that, wouldn't I have seen it while using the hot water? 

    Thirdly, the pressure relief values for both the boiler and hot water tank seem ok, dry with no water leak. 

    Is my solution to this is installing a back flow preventer for half inch copper pipe?  I cut off the hot water supply to my boiler and i have been draining the hot water tank every two hours to see how the water looks, it looks crystal clear so far, is this a one time thing? 
  • SteamheadSteamhead Member Posts: 11,378
    See my answer

    in the other thread you started on this.
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
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