Garden Valve Corrosion

The Vassar Farm Garden requires fairly heavy watering, because it’s in full sun all day long, so we lay in a set of drip lines connected through Y valves to a main feeder line running down one end of the plot. Plastic valves tend to be overly fragile, so this year I tried a few much larger full-flow ball valves with a metallic housing:

Corroded Garden Y Valve

Corroded Garden Y Valve

This valve lay on the ground (as they all do) just inside the gate and served as an occasional supply for a short hose with the hand sprinkler head. I don’t know what’s driving this corrosion, but it’s eating the external threads as well as the valve bore.

Overall, I’m unimpressed…

About these ads

  1. #1 by rkward on 14-November-2012 - 07:57

    Ed,

    Not sure of the cause either, but I do know you will have less trouble with brass … of course they will cost more. Maybe some sort of galvanic action between the zinc/die cast and whatever you have it connected to (brass?).

    • #2 by Ed on 14-November-2012 - 08:16

      less trouble with brass

      This year marks the first time Mary had trouble with thieves stealing vegetables from her Vassar Farm plot; other gardeners reported similar troubles. I fear that the thieves will discover the value of “scrap” metal in the near future, so we’re becoming reluctant to make major capital improvements…

  2. #3 by biguggy on 14-November-2012 - 07:59

    I would look for a a more noble dissimilar metal, or even graphite, somewhere close to the valve. The valve looks like it may be a zinc alloy, a piece of copper pipe or a copper fitting ‘close’ to valve may be the culprit. There is an interesting paper on the subject at: http://www.unene.ca/un1001/UN1001_Galvanic%20Corrosion.ppt (click on the ‘Quick View’) to get the diagrams.

    • #4 by Ed on 14-November-2012 - 08:12

      The valve looks like it may be a zinc alloy

      And the least expensive one they could create from random scrap, I’m sure…

      The hose fittings were all plastic: I chopped up a longer hose that we salvaged from their scrap heap last year. The end shown in the picture wasn’t connected most of the time, which means it was lying in the usual garden mulch; I have no idea what the pH might be, but it ought to be pretty close to 7. A similar Y connector a few beds away was in similar shape.

      I’ll scuff it clean and should probably give it a rattle coat of paint.

      • #5 by biguggy on 14-November-2012 - 12:50

        It does not look like ‘pitting’ or ‘chemical corrosion’ to me. Should it have been I would have expected the whole valve assembly to be corroded but the outside looks ‘pristine’ or ‘virginal’ leading me to believe that the culprit is ‘somewhere “up the pipe” and that the water is acting as an electrolyte’ not the corrosive agent in its own right. That being the case the pH of the surrounding liquid or ‘paste’ really does not matter but if you have electrolysis taking place, which I think may be the cause, that could explain the corrosion.
        I acknowledge that there are many other factors which could have influenced the situation and the details of which I am unaware of.

        • #6 by Ed on 14-November-2012 - 14:14

          the outside looks ‘pristine’ or ‘virginal’

          Somewhat to my surprise, the valve’s outside housing is chromed plastic, with metal fittings inside. The picture doesn’t make it obvious at all, but the shiny ring around the crud is part of the housing… which will linger unchanged while the metal bits fizz away. [sigh]

        • #7 by biguggy on 14-November-2012 - 15:28

          Oh! That alters my thinking.
          Thanks.

  3. #8 by Red County Pete on 14-November-2012 - 10:43

    Since fire season gets our attention every summer, we’re always on the lookout for high-flow hoses and valves. Not sure if you’d like the high-flow Nelson, but we got good service from the two we bought last spring. Plastic body and valve arms, while the ends are spring-supported hose stubs with brass ends.

    The plastic valve arms are the weak link, and the valves are a bit expensive at $15 from Home Desperate, but the ball bore is probably 1/2″, as opposed to the 5/16″ or so we’ve seen from the other wyes. If the arms die, I can make new ones. They are fairly simple and screw on the valves, though I’d probably have to deal with splines.

    Corrosion would be limited to the brass ends and the springs, with the main downsides that 1) they are about 3-4X more expensive than the zinc, and 2) they LOOK more expensive.

    Have you considered a plastic female cap for the free end? You can get these as parts for daisy-chained sprinkler fixtures. (Or use plastic quick-connects–not as robust as the brass ones, but fairly affordable and available various gender orientations–I like the female thread to male QC on the wye so I can switch back to threaded without flipping the hose ends.)

    • #9 by Ed on 14-November-2012 - 11:11

      I’ll search for Nelson valves the next time I’m at HD, but if they look as nice as you describe, that’s a downcheck for the Vassar Farm plot. I *like* brass…

      a plastic female cap for the free end

      Suffice it to say I’m not the user and fiddling with the machinery isn’t what Mary enjoys doing… she barely tolerates all the ball valve handles along the main hose leading to the beds. [grin]

      • #10 by Red County Pete on 14-November-2012 - 17:34

        She might like the QCs, though I’d strongly recommend you stay with the genders (female pipe/male QC, etc) so you can go with or without connectors. The other approach means everything has to be on QC. Melnor and Orbit sell both flavors. (muses about the sex life of a garden hose. )..;

        We use the QCs on the garden so we can drain down at night. We freeze a lot. (Zone 1, 4300 feet)

        • #11 by Ed on 14-November-2012 - 18:12

          She might like the QCs

          They haven’t gotten much traction around here, but, given the corrosion on those normally disconnected threads, I think spotting two or three for the hand-watering hose on the Y connectors along the feeder will be a Good Thing. The QCs on hand don’t have an automagic shutoff valve, so they must be on a valved Y branch.

          I may have to print larger knobs / adapters for the Y valves, too, because they’re really stiff.

          Freezing isn’t a problem here: shortly after the first freeze, Vassar turns off the water!

  4. #12 by Red County Pete on 14-November-2012 - 19:30

    Re automagic valves on QCs: check HD. Ours has some of the female QCs with a plastic valve insert–connect to flow. I got an unbranded one as part of a riding mower washout kit–similar principal to pneumatic couplers. Pretty sure Melnor and Orbit make ones like that.

    • #13 by Ed on 14-November-2012 - 19:38

      Re automagic valves on QCs: check HD.

      Obviously, I’m slated for some serious browsing…

      Thanks for the pointers!

  5. #14 by Red County Pete on 15-November-2012 - 11:02

    Had a bit of brain overload yesterday dealing with Patch Tuesday [which falls on a Wednesday] on my wife’s laptop–the local library has broadband, but it’s flaky. You only have to reverse the hoses if you start messing with the genders. With the QC-female/hose female on a hose end, you’d be good. If you strike out at HD or on-line, the John Deere garden tractors have the right [unbranded] fitting as part of the mower-deck washing kit. Ours came with the X-300 tractor. Not sure if the big-box tractor lines use the washing system.

    • #15 by Ed on 15-November-2012 - 11:39

      Ours came with the X-300 tractor.

      Now that you mention it, there’s a Tractor Supply just across the river within easy biking distance. I’ve been meaning to see what manner of toys they carry (not that we have a tractor) and this seems like a perfect justification… [grin]