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Indirect dip tube

Miata Member Posts: 17
Just a homeowner with a question based upon reading about the need to sometimes replace the dip tube on a water heater. Aside from it has always been that way wouldn't it be "better" if the cold water fill continued down the side of the tank and enter 3 inches from the bottom. Hence no need for dip tube. Just wondering.


  • Big Ed_4
    Big Ed_4 Member Posts: 2,785
    You will know when that happens ...

    There was an error rendering this rich post.

  • Alan (California Radiant) Forbes
    I agree: It probably would be better..........and more expensive to make.

    Some good quality, indirect water heaters have all the tappings on the side, with the cold water inlet at the bottom.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • Miata
    Miata Member Posts: 17
    Found part of my answer. HTP indirects pipe cold water to lower side of tank. So no dip tube. Now why not all tanks since they save on cost of dip tube?
  • Larry Weingarten
    Larry Weingarten Member Posts: 3,304
    Hi, There are things to consider. A benefit of having a dip tube with that little hole in it up at the top is that the tank cannot be siphoned down much. Should you have a water line break lower than the heater and air get into the system, even from someone in a different house opening a tap, your heater cannot drain down so that it's unsafe. If it had the cold feed at the bottom, it could be drained down that far. What if a gas burner comes on then? Or even if an electric element is no longer submerged and comes on?
    The disadvantage of dip tubes has been that plastic ones have been made poorly or have "aged out" ... gotten brittle and split from years of heat and chemical water treatment.
    Mobile home tanks often come with cold inlet at the bottom, but it seems tanks with dip tubes are inherently safer. :) Cold inlet on the tank's side should not present any safety problem with an indirect.

    Yours, Larry
    Alan (California Radiant) Forbes
  • hot_rod
    hot_rod Member Posts: 22,158
    edited March 11
    The tank stratifies best when cold flow is straight down from the dip tube. With side connections you tend to get more turbulence and tank mixing.Less tank temperature stacking and less output
    Larger tanks with side connection have a slotted sparge or diffuser tubes that lessens the turbulence in the tank.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Miata
    Miata Member Posts: 17
    That is very useful information. Where I am confused is when the cold water comes down the dip tube at let's say 50 psi and exits 3 inches from bottom, how is that different from coming in from the side 3 inches from bottom other than one discharge is down the other from the side or is that what causes the different stratification?