Hot Water recirc, replacing pump need suggestions

Discussion in 'Water Heater Forum, Tanks' started by rods, Mar 29, 2013.

  1. rods

    rods New Member

    Messages:
    2
    Location:
    Tulsa, oklahoma
    I have a dedicated recirculation system with the dedicated line returning to the bottom of the hot water heater after going through a B & G series 100 pump located right next to the hot water tank. The hot water tank is located in the downstairs recreational area but most of the house and plumbing is on the floor above the hot water heater/tank. I believe that the water leaves the hot water heater and goes along the front of the house to service those areas and then when it reaches the end of the house, it goes to the back of the house and returns back to the starting end of the house and then down to the hot water heater. The water run is about 85 feet each way. Picture the house being a rectangle of 85 feet by 35 feet. I have tried to identify the hot water flow by how long it takes to ultimately get to my shower which it seems is the farthest point. I am assuming that my head height is somewhere 10 and 15 feet. That is from the pump at the bottom of the hot water heater to a guess of how high it goes before turning toward the outlets. The ceiling is about 9 feet from the floor, so if the water is running through the floor all of the way, then 9 feet would be a good guess for the height the water has to go up.

    The existing pump (brass) has developed a leak where the motor goes into the pump housing. I have replaced the gasket and it still drips. I read a lot about just getting a new taco pump or grundfos, etc. I feel that I probably have a pump that is over sized and costing a lot to run. Also, this is about my third B & G pump but that could be related to my failures in keeping it oiled. It is a 1/12 hp, 3/4 in line, delivers 9 gpm at 8 feet, 7 gpm at 15 feet of head height.

    First questions is do I need to have a brass or stainless pump for potable water or is cast iron ok? Obviously that decision affects the price.

    Second question is can I change to a less powerful and more economical pump?

    I need a method to limit the running of this pump. Currently and since 1974 it has been set to run continually. I am not perfectly happy with a timer since it would hit the most active periods of use, but not allow for off cycle instant hot water. If I could remotely turn on the pump and have it run for 3 minutes, that would be perfect in conjunction with the timer solution. I plan to install some home automation soon and could put the electrical outlet on the system to do the timing and instant on. I only mention this in case there is a better pump choice for home automation. I have seen the aquastat features where it turns the pump off at certain temperatures even if the timer is still on, and that would be a great feature as well.

    So, please help me identify a pump that can handle the head height, the run distance, and works best with timers and aquastats. Or any other kind of suggestion for reducing the cost of instant hot water. I may for now just fix the B & G and put it on a timer, so if you can advise on what kind of time I am looking for that would be great. The electricity is right next to the pump. I am sure I have left things out, so I will be happy to answer any questions and sincerely appreciate any input.
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,002
    Location:
    New England
    Head height is much more of a consideration when it is an open ended situation - i.e., where you pump the water out, but it isn't in a continuous loop returning to the inlet. With a recirc system, the water 'falling' back down significantly aids the water being pushed (or pulled) so the head is more just the restrictions from the fittings rather than height changes. The only issue might be getting the line full in the first place (much more of an issue with heating systems and their much lower water pressure and fully closed operation than a potable system), but not normally an issue where you have the street water pressure that is more than sufficient to fill a typical residential system. IOW, a MUCH smaller pump would probably work just fine. And, code requires anything on the potable water side to be non-reactive. Things that qualify are bronze, brass (yours is probably bronze), and stainless steel). Having too large of a pump can also literally create pinhole leaks in the piping as well.
  3. rods

    rods New Member

    Messages:
    2
    Location:
    Tulsa, oklahoma
    Thank you that helps. Just being able to eliminate cast iron helps. I have had to fix one pinhole in the copper a couple of years ago. I always feared that my pump was overkill.

    Another thing that I don't understand is that if I turn off the water that runs through the dedicated return line, i.e. remove the pump. The hot water will still get to my sinks albeit in a few minutes as if I didn't have a recirc system installed. I guess I though that hot water wouldn't flow at all if that line were shut down.

    Any other thoughts or ideas are most welcome.
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,002
    Location:
    New England
    Depending on how the thing is setup, the point of return is often just a T in the hot water line at the furthest device from the tank. Everything SHOULD still get (delayed) hot water if that line is capped or blocked off. Now, a more sophisticated system may have an aquastat to shut the pump off when the monitoring point is up to temp. If you do not have a dedicated return line, then it's a bit more complex, as then it uses the cold water line for the return. This requires a crossover valve and a check valve at at least one location. Your system requires the pump and a check valve otherwise, it could be trying to pull water from both the hot (top) and cold (bottom) of the tank at the same time through the return line unless the pump could overcome that tendency. FWIW, the pump on mine is a 1/28Hp and it's moving water two stories just fine.
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