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Brown DrainBack Water

Martin RomeroMartin Romero Member Posts: 40
Solar Wizards,

My System:

4 SunEarth  4' x 10' collectors

Stainless Plate Heat Exchanger (radiant); Quad Rod Heat Exchanger (DHW)

15-20 Gallon Drain-back Tank

Unpressurized Drain-back Setup

Closed Loop

A few months after firing up my system about 2-3 years ago, I began noticing just a slight browning of the water visible through the sight glass outside my drain-back tank.  It presently looks like what's shown in the attached photo.

I'm interested in hearing your thoughts on how to proceed and how much of a concern this "browning" is.


Martin Romero


  • hot rodhot rod Member Posts: 7,085
    my guess

    would be that the system has a pump with a cast iron body. If so that is where the red color is coming from. A bit of color actually makes it easier to see the level in the sight glass.

    I prefer a pressurized drainback, but as long as it is a true closed loop, you should not see a lot more dis-color.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • Martin RomeroMartin Romero Member Posts: 40
    Browning water

    Thanks Hot Rod,

    I was certain the pump was brass, but I will double check. No real concern about heat transfer?
  • Kevin_in_DenverKevin_in_Denver Member Posts: 588
    edited November 2012
    Most likely a steel tank


    My first guess was also a cast iron pump. That tank could be steel, however. Do you have the brand name and model for it? Even if it is a glass-lined steel tank, a little bit of rusting at the fittings would be normal.

    BTW if it is a true unpressurized drainback system, that means it must be vented somewhere. A vented system usually causes a cast iron pump to fail prematurely. If it's truly a closed loop system, it will create some pressure when the air and water gets hot.
    Superinsulated Passive solar house, Buderus in floor backup heat by Mark Eatherton, 3KW grid-tied PV system, various solar thermal experiments
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