I had a pre-listing today and came across something I’ve never seen before. In one of the bathrooms, when you turn on the cold water, hot water comes out for about 5-10 seconds and then turns cold, and also when flushing the toilet the water is hot, then is cold. (Tested with Laser thermometer) Tub/shower is normal. Hot water tank is plumbed correctly.All other plumbing fixtures in the house were normal. Any ideas??? Its got me stumped.
I have a similar situation in my own kitchen…the water is warm for about 10-15 seconds in the winter months as the piping runs along the heat duct that terminates under the kitchen sink base…could this be happening there ???..jim
Thanks guys, That is absolutely the cause. Their is a radiant heat system installed under the flooring system and there are heating ducts running up the wall on same side as supply. I never even thought about that.
What about it? Certainly there is some heat loss, but it’s something I’m willing to pay for. Others may not tolerate that. Fact is, the circulator just slowly “stirs” the water. It’s not really all that much flow while it’s circulating. Just enough.
Did a consulting call on a new supposedly highly efficient home last summer. Power bills were higher than expected(only 2 occupants). Found a recirculating DHW pump for instant hot water purposes (electric tank).
In the basement mechanical room, the temp was 25 deg C (78 deg F), warmer than outdoors that day!!! I’m going to monitor the electric usage of the tank without any hot water being drawn after some other legal stuff with the builder gets out of the way. I wouldn’t be surprised that 1,000 to 1,500 watts is a constant parasitic heat loss from the poorly/partially insulated pipes in the loop.
This house has a HP/AC system. The heat loss in the summer adds to the AC costs while in the shoulder seasons of spring and fall especially, the heat loss (resistive) to the house will cause the HP not to work as much in the times when the COP is highest! This is when the HP is supposed to earn its keep!!
These may not be big energy costs individually but if you save 2-3% 10 times in a house, it adds up!
I found a small point of use water heater installed in series with the hot water source, in remote areas from the main hot water heater is more efficient than a circulating system if the building layout can accommodate the design.
There is a heat loss in hot water circulating systems, however you must consider the alternatives. The draw-down to get hot water to a remote faucet is a loss of water (several gallons) as well as energy .
The amount of water in the draw-down must be made up with cold water into the hot water heater initiating a recovery. Often the water need is small (1 quart just to wash your hands etc.) but the water usage (several gallons) and heat recovery is substantial in proportion to the need.
In my house, the water heater, laundry room, kitchen are on one side of the house and three bathrooms are stacked at the other side of the house. I installed a 4 gallon water heater below the bathrooms in series which provides near instant hot water. The cold water in the pipes to the main water heater is tempered in the 4 gallon water heater and you never feel it in the shower.
The cost of the additional piping as well as the ability to install a loop in existing construction must be considered.
The cost of a Grundfos pump (plus a timer) is as much (if not more) than a water heater. Its life expectancy is equal to or less than that of a water heater.
There was a period in history in which installers favored, due to lack of no other choice, higher volume Bell and Gosset type circulating pumps. They flowed so well, I’m sure the heat loss was much more noticible. Folks with hot water recirculation systems can normally afford to also either spring for the pipe insulation or the higher bills, so it seems like a non-issue to me. The losses from a modern, low-flow system, particularly those on a timer, are inconsequential.
Would you drink from the hot water tap? sounds like that is what you would be doing, Contaminating the cold water in the system. Is there a mandatory back flow preventer installed on the Main? or should we have the whole town drinking the Micro Organisms in our hot water tank.