Cold Water getting into Hot Water Line... Help!

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by jrrl, Feb 7, 2008.

  1. jrrl

    jrrl New Member

    Messages:
    8
    Hello.

    Last week, we noticed that our water heater was leaking a little around the base. In a rare attempt to be pro-active about such things, and realizing that the thing was at least 12 years old, we had it replaced today. The new WH is the same size as the old one (50 gallon, gas) and they didn't do anything beyond unhooking the old and hooking up the new. So, they didn't screw anything up, BUT I have no hot water.

    They noticed that we had cold water pressure in our hot water line. Indeed, if I feel the pipes, the line from the hot water heater is hot, but as soon as it splits to wander off to the sinks, etc. the pipes become at best room temperature and often cold.

    When we had a contractor finish our basement in 2002, he did SOMETHING to make it so we got hot water on our second floor (master bath) faster. At the time, I was just happy and didn't worry about it. Now, from what I've read, I believe he set up a passive loop using the return line.

    Could this be the source of the cold water? Why on earth would I have hot water with the old (leaking) WH, but not the new one? What are odds of this breaking on the same day they replacement my WH.

    The WH installers (who made it pretty clear that that is all they do... serves me right for calling a specialty shop, I guess) suggested that the source could be a mixing valve somewhere. If I cut all water to the washer, no change, so that's out. The shower in the basement (only 6 years old) DOES have a single handle control, but when I cut all water to that bathroom nothing changes. Would a dishwasher have a mixing valve?

    I did find the return line and it connects to the cold water line as it leads into the WH. But when I closed the valve on the return line, again, there was no change.

    I am at my wit's end. My poor kids had to take a room temperature bath tonight. I don't even know how I would find a decent enough plumber to solve this riddle (we've had bad luck with plumbers in the past).

    Any ideas would be incredible.

    -John.
  2. Terry

    Terry Administrator Staff Member

    Messages:
    15,416
    Location:
    Bothell, Washington
    If you have a digital camera, you can add them to the post, maybe we will see why it's not working.
  3. jrrl

    jrrl New Member

    Messages:
    8
    Digital camera's at work. I'll see if I can grab it in the morning. What would you like pictures of?

    -John.
  4. Herk

    Herk Plumber

    Messages:
    547
    Location:
    S.E. Idaho
    I'd start with a little testing. First, have someone turn on a kitchen faucet or something while you feel the pipes coming out of the heater. If the hot side gets hot that part's OK. If the cold side gets hot, that means that it's hooked backwards.

    Then, check to see how far the line gets hot. If you can see enough of it, maybe it tees off somewhere. Also, see how hot it gets. If the dip tube is broken or missing inside the heater, water can cross from the cold side to the hot side and you may get a tiny bit of hot before it begins to chill.

    And we assume that the pipe above the heater feels hot before you start to run water. The water heater may be set very low - they come from the factory at about 120 degrees or less and because of liability some plumbers will not raise the temperature though they might show the customer how to do it.
  5. fidodie

    fidodie New Member

    Messages:
    94
    Location:
    new jersey
    just fyi: dishwashers are usually hooked to only one water source - hot or cold (yes, mine actually recommends hooking to cold, as it boils the water anyway)

    where did they hook up this return loop? take a pic of that!

    if you turn off the supply valve to your hot water heater, is there still pressure at the hot taps (preferably a dedicated hot valve to check it)? thus cold is somehow hooked to hot in other places (i noted somewhere else where i had a test cap on a shower mixing valve, and that allowed cross flow between the hot and cold)

    my parents house had a cross over valve to mix cold with hot, so you ran the small tank at a very high temp, but immediately mixed in cold to "extend" the size of the tank (and not blanche the kids). perhaps they fully opened this antiquated cross-connect? it would be a connection that bridges the hot and cold above the water heater with a valve. newbie helper with installer may have opened it?

    any other renovations going on in the house?

    electric or gas (or other) WH ?

    open the drain valve on the bottom of the wh and see if the water comes out hot.
  6. jrrl

    jrrl New Member

    Messages:
    8
    Update... okay, we actually have three problems, it seems, one of which has since been fixed.

    1) The installers soldered too close to the top of the tank and fried the valves. Okay, new tank. Let's try again. Yes, hot water! Not as hot as it should be, maybe, but it is a major step in the right direction. But there is still cold water in the line as well, because...

    2) The cross connect seems to be (i.e. we can't find any other explanation) due to the passive return without a check valve. I am not sure WHY we are getting that much backflow, but we definitely are. The plumber was going to install a check valve, but...

    3) Our main valve for the house doesn't quite turn off all the water. So, they can't get a dry pipe to solder.

    So, we have hottish water, but not as much as or as hot as before (still not sure what the heck changed... maybe the BTUage?), but we need to get the water company to shut off our water at the street to get the backflow fixed. Which SHOULD (we think) fix the problem.

    Does ANY of this make sense? The hot line is 3/4", but the return is only 1/2", so I don't know why we are getting so much backflow. Any thoughts? My wife would love to take a real hot shower again.

    -John.
  7. fidodie

    fidodie New Member

    Messages:
    94
    Location:
    new jersey
    simple test -
    buy a $20 shark bite ball valve, jam it on the passive loop down by the tank, and shut it off. if that solve the hot problem, then the cold is travelling down the dip tube, and up the passive loop. you can then make up your mind if it should be capped, or install a shark bite check valve!

    how is water coming down the passive loop if the hot water tank wasn't filled? did they install a new shut-off at the tank, if one wasn't there?
  8. jrrl

    jrrl New Member

    Messages:
    8
    You are assuming I am brave enough to screw with my own plumbing. I've made too many mistakes in the past... I just want to know what to tell the plumber. I UNDERSTAND plumber, but I tend to have leak problems if I try to change it myself. :-/

    Here's a diagram of how the hot (red), cold (blue), and return (purple) are all connected above the water heater (grey) and ball valves (er, also grey)...

    Is this connected wrong? My thought was that a check valve where the return connected to the cold would solve the problem.

    Thanks again to everyone trying to help this analytically sound, but water challenged homeowner.

    -John.[​IMG]
    Last edited: Feb 9, 2008
  9. fidodie

    fidodie New Member

    Messages:
    94
    Location:
    new jersey
    chart didn't make it! - Never Mind - it is there now!
    can you post a pic ? pm me if you need to mms it to get it off a cell phone.

    i've never heard of a passive loop not hooked into the bottom of the tank, loops with pumps have check valves and are hooked to the cold inlet to simplify the tank connections.

    i'm still amazed a plumber actually used water as an excuse, unless they were standing in it!
  10. fidodie

    fidodie New Member

    Messages:
    94
    Location:
    new jersey
    that also explains why there is cold water in the hot when shut off , the return should be T'd in after the valve. that way when it is shut off, there is no water feeding that side of the system.

    This will not work! The check valve will render the return loop inop in a passive system.

    was it this way in the old system? or was the return plumbed into the bottom of the tank?

    your installer changed something, because if they only changed the tank, they would have shut off the two valves, replaced the tank, and never knew the main was leaking......

    asks them to send out the boss.
  11. jrrl

    jrrl New Member

    Messages:
    8
    So, should the return be going into the third hole on the top with a dip tube? Is there already a dip tube in there or does the plumber need to install one? Or is there some place on the bottom of the outside of the tank that I can't see?

    [​IMG]

    [​IMG]
  12. jrrl

    jrrl New Member

    Messages:
    8
    Actually, the original plumbers are no longer welcome in my home. They were very unprofessional when here and refused to acknowledge that they had fried the valves (despite there being clear signs that they could not have done otherwise). There have been some fairly long and heated conversations and they are adamant in refusing to do a damn thing. I needed hot water so I called someone else. Serves me right for calling someone cheap instead of someone better known. My bad.

    The way they discovered that there was cold in the hot lines is that they wanted to drain the line of all hot water (for whatever reason) and even with the WH closed off, there was plenty of cold coming out of the utility sink.

    That said, neither installer changed anything, so maybe our old WH was just super magic or something. In any case, it isn't working correctly now. But if it as simple as disconnecting the return from the cold and attaching it to a dip tube in the tank, I will be a happy camper!

    -John.
  13. jrrl

    jrrl New Member

    Messages:
    8
    Wait. That third hole is the anode rod, right?

    So, I need a check valve on the end of the return? Or is there some clever way to get the water to the bottom of the tank other than parasiting off of the cold water feed?

    -John.
  14. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,319
    Location:
    New England
    Some people put a t on the drain valve and run the return in there. The dip tube is on the cold water input.
  15. fidodie

    fidodie New Member

    Messages:
    94
    Location:
    new jersey
    yes, the way to do it is with a T off the drain at the bottom. If you cann't live with the hot water delay, try the shark bite check valve - you don't need to solder, just cut, and insert (in the correct direction) - minimally, it will keep the cold from going up the hot, even if it prevents the hot from returning down the line (thus the delay returns)

    do it on a tuesday morning, just in case you need to call someone....

    of course if you cann't shut the water off at the main, it may be a bad idea - the shark bites don't need to be dry either, they just push on and done.

    i really have no idea how it managed to work before!
    while the plumber is there, have him/her fix the valve(s) at the mains. they'll have the tool to shut it off at the street on their truck. of course if the utility sink is below the WH lines, you may be able to open the valves there, and stay dry while the mains are closed (but leaking)
  16. jrrl

    jrrl New Member

    Messages:
    8
    Okay, so they need to attach a T to the drain and then one branch become the intake for the return and the other gets a new stopcock and becomes the new drain, yes? Presumably the originally drain just stays open all the time.

    I always need to call someone... Water and I don't mix. Phone lines and electric I can do, but water pipes and I are not friends.


    I think in the city (Pittsburgh), the city has to turn off the water at the street. Just to make life difficult. That said, i will definitely have them replace that valve so I never have to deal with the city again.

    New Question: What if, instead of T-ing off the drain, they added a check valve near the end of the return (so no cold goes up the hot line) and a check valve between the branch and the return (so no warm goes up the cold line)?

    I'm just thinking that I'm going to have to convince the plumber (who seemed baffled by the return thing without a valve) to do this. Adding a couple of valves will seem at worst like a waste of time to him/her (him if I can get the same guy, since he almost seemed to understand it). Tee-ing off the valve may seem like spooky voodoo if they guy is mechanically good, but clueless. Am I making any sense?


    Oh, I just saw this thread where they end up needing a check valve on their return which puts too much resistance in the line so then they have to add a recirc pump... is this something I should be anticipating?

    Oh, btw, stupid question... if the return is NOT pumped back into the hot water heater, where does it go? Does it just get capped off? Frankly, I would rather have a wait a minute for solid hot and instant kind-of-hot-but-not-for-long... (not sure my wife would agree tho) still wondering why it all worked with the old WH...

    -John.
    Last edited: Feb 9, 2008
  17. fidodie

    fidodie New Member

    Messages:
    94
    Location:
    new jersey
    Appreciate your honesty assesment of your plumbing skills!

    yes, a T would be placed between the WH and the drain cock, and the return would be plumbed into it. the T at the cold water pipe would then be capped.

    The last 6 feet of the return line is left uninsulated - this temp difference causes the water to cool, become more dense then the water in the tank and "fall" pushing water out the top of the hot loop - I never goes into the cold, because it would always have less pressure - the hot and return, are slightly out of balance, thus fluw.. if i remember my fluid dynamics, you do not need a check valve because it is a case of water finding its own level (the cooler water in this case) and won't go up the return, when the lighter water can travel up the hot side. (i assume there are situations where this is not so - like water heater top above the fixture - in which case it would flow out the bottom ?)

    your water meter should have valves on both sides of it. then the meter can be serviced without needing to be shut off at the street and/or draining the house. That may be current code too.

    adding the recirculator with timer could save you in the long run - the timer doesn't run the loop while you are sleeping or away from home. it could be plumbed into the top of the WH.

    If you really just want to have a warm shower, and can live with the delay, just put a check valve in the return where it is. I would worry about just capping it off, since it would have stagnant water in it. the cold flowing by would pull some hot through, keeping it from getting nasty.
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