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New to Me Indirect, how should I clean it?

SuperJSuperJ Posts: 478Member
I picked up a used Weil Mclain Ultra 40 indirect tank. It's probably about 5 years old and seems to be good shape.
Before I put it into service (in my house), any recommendations for any cleaning descaling I should do?
It's hard to say if it needs it or not, but once it's installed, I plan to leave it there for the next 15-20years.


  • Larry WeingartenLarry Weingarten Posts: 1,461Member
    Hello, I might give it a good rinse. Perhaps take some small diameter aluminum tubing hooked up to a hose and use that to spray around on the inside of the tank, while tipping the tank so it flows out the drain port nicely. I'd do this possibly messy work outside. I also wouldn't use any strong chemicals as they could damage the passivation coating on the stainless. ;)

    Yours, Larry
  • hot_rodhot_rod Posts: 11,259Member
    I think that is a tank in tank design, the triangle Tube style. You may need to tip it over or on it's side to flush any sediment out, they didn't typically have a bottom drain port.

    Do you have one of those small flex cameras to look down inside and see how it looks? If it has a lot of mineral scale you might need more like a carwash flow and pressure to flush.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • HVACNUTHVACNUT Posts: 2,036Member
    A TT tank might have other ideas than to stay around another 10-15 years. But if you got it on the cheap, no harm, no foul.
  • SuperJSuperJ Posts: 478Member
    You're right. No bottom drain port. I wondered if was tank in tank. Thanks for the warning about chemicals.
    Yes, I got it cheap. $200 for the tank and a bunch of new/used panel radiators.
    Is actually a rebranded TT tank or just a similar design?
  • hot_rodhot_rod Posts: 11,259Member
    I believe it is a rebadged TT, or made by the parent company of TT.
    Does the label say made in Belgium?

    They were notorious for low pressure drop with a tank in tank design,easy to move a lot of flow thru, but heat exchange was somewhat compromised by inlet and outlet locations.

    I had a horizontal version TR 40 in my own house for 10 years or more. Still worked fine when I upgraded to a solar tank with dual coils.

    Like any metal tank, the amount of water, quality of water and service routine add or subtract from the years.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • ZmanZman Posts: 4,812Member
    Be very careful of the fill and drain sequence with the TT design. It would be very easy to accidentally crush the inner tank or break the connecting welds. Take a look at the fill instructions in the manual as well as the cutaway picture of the design. You never want to fill the inner domestic tank without filling the outer boiler water space first. Tipping the tank with fluid inside would also be very bad. The inner tank needs to be siphoned to empty.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • SuperJSuperJ Posts: 478Member
    It is made in Belgium. Hopefully it's not already damaged.
  • delta Tdelta T Posts: 743Member
    @Zman took the words out of my mouth. Be GENTLE. It is a royal PITA to get all the water out of those, and even if you leave 5 gallons, that is still 40 pounds on a 4' lever that you are swinging around. If I remember correctly the inner tank is supported at the top by the cold and hot nipples and is suspended from there, that weld can crack easily.
  • SuperJSuperJ Posts: 478Member
    Yikes, I transported it on it's side to my house. I think there was less than 2 gallons remaining in there. I guess I will do a pressure test before I haul it into my basement.
    Weird they wouldn't put some sort of support ring/brackets around the lower portion of the inner tank to brace it against the outer wall.
  • Jean-David BeyerJean-David Beyer Posts: 2,609Member
    I have one of those. Installed April-May 2009.
    Only problem so far is aquastat failed demanding heat. P/T valve operated as it should, so a water mess on garage floor.

    Installation instructions are very strict: fill the outer tank first, then put domestic water in inner tank. So the weight of the water in the inner tank need not be supported by the pipe fittings at the top. There is one domestic water supply fitting on the top, and two output ones. My house and the P/T valve are in one, and the other, marked Auxiliary, has a shutoff valve and a cap. Inside is a dip tube that reaches most of the way to the bottom of the domestic tank. So you could probably siphon water out down to there. I suspect that the dip tube from the water supply is a little longer than that, but I am not sure. So I do not know how to fully empty the inside tank.

    The outer tank has the hot water supply near the bottom, and the return from near the top. So you should be able to get a lot of that water out.

    As far as heat transfer is concerned, where do you suppose the scale would be? On the outside of the inner tank, or the inside of it? I must assume on the inside, but how hot does that tank get. Probably under 200F, right? It is not like there is fire there. I understand that the inner tank can expand or contract. If it does that, that should flake any scale from the tank and it should fall to the bottom. Maybe.

    Mine is made in Belgium, is branded Weil-McLain, and I understand it is actually Triangle Tube. I run it at 140F (wanders up to 160F because of the aquastat differential) and mix it down to 125F as it enters the house with a pressure-temperature balancing valve. The maximum I get from the nearest tap is 120F.
  • hot_rodhot_rod Posts: 11,259Member
    Most scale would be on the inside of the inner tanks as it sees constant fresh water added. There may be some scale on the outside from the fill water in the boiler loop. As long as that is not changed or replenished often the metals touching the boiler water should not be scaled badly.

    Scale, minerals that fall out of solution, accumulate on the hottest surfaces, and the ones in solution settle to the bottom of the tank eventually.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
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