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Below the water line, wet return rust build up.

Maine VentMaine Vent Posts: 129Member
I just officially did the summer draining and flushing. All went well with that. I removed my great hallway radiator because I putting in a new floor in that room. Here is what I discovered. The radiator is one of my 2 pipe radiators. The return line where it is piped into a floor return header I felt was somewhat clogged with rust and debris. My conclusion was to add water to my empty boiler and see if this added water would come out this open pipe return header. No water came out. So probed the hole with my finger, black sludgie water came out. I found a long thin brush and stuck that in hole and cleaned what I could. This is a 3 year old system, cleaned and flushed from 4 different point on the system. The discovery was only made because I took out the radiator. My concern going forward is keeping this wet return header clean and flushed out. This is a major condensate return for boiler water. So i after my brushing of the hole, I added water very quickly and it seemed to flush out the dark brown residue and then it cleared out to fresh water.

Anyone have any suggestions on trying to keep the pipe rust down. Not a big fan of chemicals, but I am open to any kind of a safe additive that will help with keeping the rust sediment down.

Long cold winter here in Maine, I'm one guy who's glad to shut this thing off for a while.

Thanks for your time and advice.


  • FredFred Posts: 8,279Member
    More info needed. I'm assumming this is a two pipe steam system? I'm not sure what you mean by a "return header". Do you mean a drip leg or a trap of some kind? A few pictures might be in order.
  • Maine VentMaine Vent Posts: 129Member
    Hi Fred,
    I have "combo" system, 4 two pipe rads, 5, 1 pipe rads. What I mean by a return header is. I have 1 large diameter wet return, and 3 small diameter wet returns that all converge into 2" return line that looks like small version of a header.

    Anyway, back to rust buildup. 3 year old system that is cleaned very well. It looks to me like these condensate returns bring a lot of crap rust back to the boiler.

    I, for one, have seen the damage that water and air can do these systems. Is there any seasonal treatment that can be used to put the boiler into a state of coated pipe lining to slow down the rusty clot build up?

    Thanks Fred
  • Jamie HallJamie Hall Posts: 12,145Member
    Is this particular pipe a "real" wet return? That is, is it below the boiler operating waterline? Or is it actually a dry return? If it is a dry return, make sure that it really has enough pitch to drain -- thoroughly and completely -- when the system is not making steam. If, on the other hand, it is a wet return, there will be relatively little rusting -- while it is under water.

    If this is a system which you drain in the winter (it almost sounds like it) it is very difficult to avoid rusting, as the combination of air and moisture is pretty tough on pipes (or any iron, for that matter!). The best bet is to not only drain it, but open any plugs or drain valves -- anything that can be opened -- and leave it that way. That will at least slow it down...

    As to chemical additives -- they won't get into either wet or dry returns, as they don't get into the steam.
    Br. Jamie, osb

    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
  • FredFred Posts: 8,279Member
    The very nature of radiators/ return piping and wet returns is that they are exposed to water and air virtually 100% of the time. Most of that sediment in the wet returns is from the mains, radiators and dry returns. It sounds like you have several locations where you can flush out the wet returns and that is probably something you should do at the end of a heating season. You may want to check the PH of the water in your boiler/wet return and maybe add something like one or two Steamaster tablets to your boiler water to help keep the PH in the 8 to 9 range. (Just 1 or 2 tablets. Don't use the amount suggested on the bottle. It way too much) Whenever you add water to the boiler or drain/flush it, always run the boiler long enough to bring that water to a boil to remove any excess oxygen in the fresh water. Keep in mind, the boiler and maybe the wet return is only 3 years old but the radiators the main(s) and probably the dry returns are as old as the house. Mine are 115 years old and still going strong but there will always be some sediment that needs to be cleaned out at reasonable intervals.
  • Charlie from wmassCharlie from wmass Posts: 4,111Member
    I try to isolate the return pipe and allow the condensate to fill them instead of raw water back feeding from the Hartford loop. I also pipe my feed water on the boiler side of the Hartford loop.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • nicholas bonham-carternicholas bonham-carter Posts: 8,084Member
    Charlie, can you elaborate on that return piping a bit?--NBC
  • JUGHNEJUGHNE Posts: 6,535Member
    I just replaced most parts of a wet return (manifold as you describe it) right at the boiler. 14 year old nipples (maybe Chicom brand had pinholes; fittings (USA) unions were good but tee & 90's threads were slightly eroded.

    It was re-piped with a cross fitting and plugged tees so as to easily wash the wet return with the cleaning wand used on the boiler. A 6" drip leg was also included on the wet return as the primary collection point. A floor drain was just in the right place, thankfully!

    The wet return being the lowest point of the system collects all the junk from the dry returns. The junk would have rise up to flow over the Hartford Loop to get to the boiler. By cleaning the wet returns every year the boiler would be protected from most of the sediment collected there.

    You might consider just cleaning those pipes this year and look again after one season of operation. In the case above the returns had never been flushed since the boiler change of 14 years ago.

    One might consider the wet returns at the boiler as "sacrificial piping" to be changed every 25 years or so.

    As Jamie pointed out to have "dry" returns stay dry after a boiler firing cycle; all need slope to drain back to wet return. On this job after most of a day in a crawl space rehanging/sloping all 300 plus feet of piping (supply & return) the boiler sight glass gained nearly an inch of water which had been sitting in pipes that should have dry (supply included).
  • Maine VentMaine Vent Posts: 129Member
    Thank You for the suggestions, I guess as long as I get a good flush from all the lines, and then flush really good at the boiler. because this is where all this crud will collect.
  • JUGHNEJUGHNE Posts: 6,535Member
    Do you have a washing wand for your boiler that would go into any cleanout fitting on the wet return??
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