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Frequent replacement of black pipe nipples and other fittings.

galileogalileo Posts: 5Member
In the past few years, I've had to replace several nipples and fittings in my low-pressure steam heating system. An old timer in my area has told me that it's because of the cheap steel that comes from China that may contain many impurities. As well, I have recently been told that using pipe dope on threaded fittings will decrease the life of the fittings since the pipe dope reacts with the hot steam and the chemical reactions caused by the process will "eat away" the black nipples and tees etc. especially the threads. I have had to replace several black pipe fittings in the past few years. Some lasting only one or two years.
Any thoughts on whether the pipe dope could be contributing to the premature replacement of black pipe fittings?
The pipe dope I use now is grey in color.



  • nicholas bonham-carternicholas bonham-carter Posts: 7,132Member
    How are the nipples failing?
    Are the failing nipples below or above the waterline?
    I doubt that any pipe dope able to eat through steel would remain on the market for long.
    Is your water pure and clear in the sight glass?—NBC
  • ShaneShane Posts: 120Member
    Does your steam boiler have an auto fill? If you are adding more makeup water than before, it will eat steel pretty quickly. I would check all connections, even packing on radiator valves (which can evaporate before you see them)
  • EBEBRATT-EdEBEBRATT-Ed Posts: 3,857Member
    It's not the pipe dope. excessive mu water will do it. I would take a water sample and have it tested. You could use schedule 80 nipples much thicker
  • galileogalileo Posts: 5Member
    Hi Ed, I have considered schedule 80 nipples and pipes. Now that I know it's not the pipe dope I will order more schedule 80. I will have the water tested as well.
    appreciate your input
    Thank you kindly
  • MilanDMilanD Posts: 1,101Member
    I am assuming this is in the wet side of things, yes? I had a similar issue on my pumped boiler feed line, in the 2" equalized side, capped dead-end nipple off the bottom of the equalizer return. The only thing I could surmise was that the seam inside the nipple in combination with pumped flow and muck caused water turbulence and this particular pipe erosion. I caught it before it leaked as I removed the nipple to wand the boiler. But, wow... So, schedule 80 it was as a replacement, and I throttled down the feed via a valve, which it previously wasn't done. Will see how long this lasts.
  • galileogalileo Posts: 5Member
    Milan, yes, it's on the wet side of the system. We have very hard water in my area and even though the boiler is fed via the hotwater tanks, thus reducing the hardness to some extent, I have to clean out all pipes and controls every few years on account of the constant hardwater residue in the system.

  • nicholas bonham-carternicholas bonham-carter Posts: 7,132Member
    edited May 21
    Is the hot water softened?
    We have unsoftened water, and it seems that the whole hot water distribution system including taps, gets limed up more than the cold side.
    Depending on the size of your boiler, only a few gallons of makeup water should be needed for each season. Do you know how much water you have to add?
    Oxygen in fresh water is the real danger to cast iron.—NBC
  • MilanDMilanD Posts: 1,101Member
    edited May 20
    Where in the system is the failing nipple and fittings located? If this is on the side after the pump for feeding the boiler, try throttling down the flow with a valve. Those pumps should be throttled down anyway, to avoid stem collapse while the boiler is making steam by introducing makeup water at a slower rate. This will also slow the flow and possible eroding effect of turbulence. Worth the shot.
  • Jamie HallJamie Hall Posts: 8,117Member
    I'm very concerned about your comment on makeup water. As several have said, excessive -- which I would count for the average residential system as anything over a gallon a week (perhaps a little more in really cold weather) -- makeup is just lethal on the wet side of the system. Find and fix any steam leaks! Or vents which leak, or...

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • galileogalileo Posts: 5Member
    Hi Jamie,
    I have a 600 thousand BTU Weil McLean boiler which I flush down on a weekly basis. I open the 4 valves on the boiler starting from the top down and I would say that I definitely flush out more than a gallon each week. I don't have a water softening system for my building but feed the boiler via two hot water tanks, thus hot water feeds my boiler. I was told many years ago that I should flush the controls on the boiler on a weekly basis. I have also throttled down the water feeder line from the pump to the boiler in order to reduce turbulence.
    Every heating season I have several leaks in the water lines in my system. Like I said, the black pipe available lately is not as good as it was years ago. Too many impurities are introduced through the use of recycled metal in the smelting process is what I was told.

    Thanks for your input.
  • nicholas bonham-carternicholas bonham-carter Posts: 7,132Member
    What valves are you opening here? The weekly flush of the LWCO should suffice: (open drain valve until running clear).
    You could do a monthly flush of the boiler drains to remove any accumulated sediment.
    Opening all the valves once a week might introduce 4 or 5 gallons of fresh oxygenated water into a system which may not fire for a few hours, thus exposing those thinner pipes to corrosion.—NBC
  • GBartGBart Posts: 211Member
    You should have some way of metering your fresh water intake as well, Hydrolevel makes one or on large systems people use a standard water meter, we usually put them on cooling towers as well, you could be taking in a lot of fresh water.
  • You may have some stray electricity causing electrolysis, I've never seen a nipple wear out in two or three years, and I buy them from all different places, something else is going on here. Is there an automatic feed for the boiler? How many sq feet is the building?

    Thanks, Bob Gagnon
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • RomanPRomanP Posts: 46Member
    Well, according to chief here @Dan Holohan minerals in hot water are more aggressive than in cold. I always feed my boilers using cold water. Now if you have leaks in the system, bad water, which is constantly getting added to the system at high temperature, with fresh oxygen... that could do some damage.

    I’ve never encountered such an issue, with nipples rotting out

    Good Luck
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