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Dirty Steam Water in Hot Water Tank

nycpa
nycpa Member Posts: 108
Hi,



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. 

Comments

  • Rod
    Rod Posts: 2,067
    Back Flow Preventer

    You should have a back flow preventer on the cold water line before the boiler auto water feed.

    Here's a link to the Watts model:

    http://www.pexsupply.com/Watts-0063190-BBFP-1-2-IPS-Backflow-Preventer

    You should also be able to get one from your local plumbing supply.

    - Rod



     
  • nycpa
    nycpa Member Posts: 108
    Steam water in hot water tank

    Thanks for the response Rod, I just had another question, the picture of the back flow preventer has three openings, where does the opening in the middle go?  Should I install this in the main line right before the auto feeder with a shut off valve right before it?  I shut off the water to my boiler and have been draining the water every two hours, it looks clear now,  could this have been a one time thing?  
  • Rod
    Rod Posts: 2,067
    edited September 2013
    Back Flow Preventer

    Hi- The “middle opening” is a vent port and should have a pipe leading downward similar to the vent pipe on a boiler safety valve. I’ve attached a info sheet which shows typical piping.



    Is this a “one time thing” ? - Probably, at least to the extent where the amount of contamination discolors the water. However that doesn’t mean that small amounts aren’t continually being bled back into your hot water heater and into your domestic water system.  Most modern codes require a back flow preventer to prevent cross contamination and it is cheap insurance to help preserve the long range health of your family.

    - Rod
  • ChrisJ
    ChrisJ Member Posts: 13,914
    Backflow preventer

    While a backflow preventer is required in most areas by code I doubt it will ever do anything on a steam boiler.



    Typical water pressure for portable water is what, 20-80PSI?  If your steam pressure ever exceeded 15PSI the pressure release on the boiler would have popped.  I don't see any way water would have made its way from your steam boiler into the domestic hot water heater.



    Have you checked your water's PH lately?  Do you have well or city water?  When was the last time you checked the anode rod in the water heater? 
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • Steamhead
    Steamhead Member Posts: 15,773
    edited September 2013
    Sure you didn't

    just stir up a bunch of dirt that was already in the bottom of the water heater?



    Has the heater been gurgling or popping when the burner is on?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • nycpa
    nycpa Member Posts: 108
    Hot water heater

    The hot water heater seems normal.  The last time I cleaned it was last year.  The dirty water looked exactly like the brown water that comes out from the steam boiler when i drain the water to clean it.  I just didn't understand how water could force its way from the water supply line to the steam boiler, up against consent pressure and into my hot water tank then settling into the bottom of the water.  I will now clean my hot water tank every week and install the back flow preventer that Rod mentioned.  Hopefully this will solve it.  I have water supplied from the municipal.   
  • Rod
    Rod Posts: 2,067
    Possible Backflow

    Hi- First I must emphasize that since I wasn’t there and able to look at your piping, I can only theorize what may have happened. As others have said it may only be normal ”dirt”that has settled  over time in your Hot Water tank.



    My thoughts were that you mentioned that you opened  the “by pass” valve to speed up the filling of the steam boiler. This action would  have "by passed" the check valves in the auto water feeder so that it was now possible for fluids, in the water pipe to the steam boiler, to be able to flow both ways, either in to or out of the steam boiler.



    The next thing to consider would be how the above mentioned pipe to the boiler connects to the domestic cold water piping. If it tees off the cold water line to the Hot Water heater and there was water flowing in volume through the tee to the water heater, the tee might create a siphon that would “pull” dirty water from the steam boiler. (This is what a backflow preventer’s job is to stop.)  

    Normally this probably wouldn’t happen, it’s just with the combination of the pipe to the boiler being open and work being done on the HW heater at the same time, may have created the situation for this to happen.  Does this even seem like a reasonable possibility for what occurred or would you like to hear my theory on space aliens messing with your cold water system?! :)

    - Rod
  • nycpa
    nycpa Member Posts: 108
    Thanks

    Thanks Rod, I think it was definitely the by pass that did it, i never opened it before just waited the usual ten minutes for it to kick in.  But the backflow preventer was a good idea i don t know why the person that put in the water feeder didn't think about it. 
This discussion has been closed.