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What IS this white crud?

Empire_2 Member Posts: 2,343
Yea,...That's probably pipe dope circulating thru the system. I would put on a small "Y" strainer so you can clean it periodically.

MIke T.


  • Charles_8
    Charles_8 Member Posts: 74

    What on earth is this white stuff that keeps clogging the flap check valve in my external-storage "tankless" coil system?
    It's soft, but enough to gum up the flap so it doesn't completely close and reverse thermosiphoning overheats my water. (Today I put in a Stadler 20201 spring check valve instead, and also a Watts mixing valve, so hopefully no more excessively hot water at the taps).

    Anyway I don't know what it is, but it always accumulated only in that valve. It has no taste, so it doesn't seem to be a salt (i.e. a chloride). Any ideas?

  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928
    Do I see tails?

    Cream of teflon? (pipe dope & teflon tape)

    Tasteless? Have you considered sending that pipe to Fear Factor?

  • hot_rod
    hot_rod Member Posts: 21,862
    Check your hardness

    on the supply water. It looks like the minerals that fall out when water is heated. Same stuff that drains out of the bottom of water heaters. let it dry and it looks like lime or calcium.

    The higher the temperature the more hardness precipitates out. And it will hamper the heat exchange of the coil. less output, longer run cycles, etc.

    A water softener may be the best cure. Installing filters or strainers will only move the problem to another area.

    Start with a hardness test.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Empire_2
    Empire_2 Member Posts: 2,343
    hot rod,...agreed.

    The only problem is the calcium tends to be evenly distributed in any opening, orifice etc... Also if it were calcium, you would see it in the form of hard minute particles that form over time. That's the only reason I think it's dope from the system. This is soft and mushy if that's a good word to describe it:-). Checking the water quality is a great idea and that would give the untimate explanation of what this stuff is. I still think it look's like cus-cus.........:=)

    Mike T.
  • Derheatmeister
    Derheatmeister Member Posts: 1,515

    I see this on Waterheaters with Municipal water supply,never on well systems, It has something to do with the additives that they put into the water..i.e. Chlorin ..

    Is it Slimy White/Green/blueish Paste that fills up the bottom of the waterheater?.. If so, it was explained to me (By a former boss) that when the water is heated it "released" from the water...

    Call your water comp. and ask them about this.HM.
  • tim smith
    tim smith Member Posts: 2,738
    Did you have a fair amount of copper pipe work done??

    Looks almost exactly like Oatey flux. I would think a serious flush of system might clear it. Good luck.
  • john_180
    john_180 Member Posts: 2
    white crud

    does this tank have a dip tube in it?i've seen some older tanks maybe ao smiths that had dip tube on cold inlet that broke down and clogged drawoffs and check valves
  • Larry Weingarten
    Larry Weingarten Member Posts: 3,236
    You might...

    ...try cleaning the goo off of one spot and then having a close look at the metal there. If it is showing any sign of corrosion in that spot, the white goo could be byproduct of pitting/crevice corrosion. Aluminum anodes produce similar goo as they do their job, though generally it's a bit grayer. Put the goo you removed out to dry for a day or so. If it turns to dust, it's more likely anode, corrosion or hard water residue than flux. I'd vote for that water test as a good place to start.

    Yours, Larry
  • Dezincification ???

    When it does that on the outside, it's called dezincification.

  • Charles_8
    Charles_8 Member Posts: 74
    I let it dry and...

    ... the "pellets" are still very soft, and crumble easily into a fine powder when gently pressed with a fingertip.

    The city water is indeed quite hard, although I have not had it tested yet. This doesn't seem to be the same crusty whitish buildup that forms in sinks and tubs, though.

    I did the installation myself at the end of July 2007, using a brand-new Whirlpool 40 gal electric heater as the storage tank. Cold plumbing is CPVC, but all the hot water lines including the recirculator loop are 1/2" copper. So there are lots of solder joints. I have been using Teflon tape to seal the threaded adapters. This is definitely some kind of mineral, not a "string" of sealing tape cut from a thread.

    Maybe it is the flux after all. I guess the only way to know for sure is to have the water, and the mysterious "couscous" tested at a lab. Anyone know of one?


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