A mystery to me

[fptahoe]

We bought another house and it has a hot water circulator on the hot water tank to insure that hot water is delivered very soon after any of the faucets in the house are turned on.  Right after we bought the house, we noticed that when you turned the COLD water on, it would deliver hot water for about a minute.  I don't mean warm water, I mean you-can-barely-hold-you-hand under it hot.  Called a plumber who said he could not figure out why it did that, but we turned off the hot water circulator (or what ever it is properly called).  The problem - hot water for about a minute after turning only the cold water on, persists even after disconnecting the hot water circulator.  Every faucet in the house has the same issue.  The reason for this post is to see if anyone has any idea what is causing this and how it may be remedied.  I have Kohler faucets throughout which all seem to be in good working order.  Open to any and all ideas.  Thanks as always....FPT.

[blackhat]

Can you post a pic of the pump install? If not post, let me know and you can email it to me.

[Bob10]

strange that it happens at every sink the Laing autocirc uses a cross over usually at the sink furthest from the tank.  You open the valve and the pump pushes the water to the cold line until the thermostatic valve in the crossover closes

[Mr_Mike]

As a guess: Bad thermal valve plus convection loop?

Or, the plumber didn't actually disable the pump or there is a second pump that is not yet found. There can be pumps near the heater and pumps at the farthest fixture location.

[rwe2156]

Not a fan of hw recirculators.  Energy wasters.

Instant hot water heaters or a secondary hw heater are better solution.

[Bob10]

The autocirc models have timers and while they use a bit of power they save a lot of water

[Robert Adams]

Not a fan of hw recirculators.  Energy wasters.

Instant hot water heaters or a secondary hw heater are better solution.

Yeah water is cheaper than electricity or gas. Those type recirculators just add allot more water for the heater to heat. 

   I however do like the manual recirculators that have a button to push. Basically push the button and the hot water is there immediately. 

    A seccond unit though would just add to operational costs and instant waterheaters are well endless hot water which is not a good thing. The small 110v ones are nice for a place where you can only get cold water to and just used for hand washing.

[woodhead]

Can you make a riser diagram of your HW and CW lines, showing the Water heater and pump?  

Just Askin? 

 Look at the sink piping furthest from the water heater.


Al

[goaliedad]

Are the hot and cold supply lines really close to each other? Especially near the sinks?
I am wondering if heat is being transferred to the cold line

Also is the water that first comes out if the cold faucet hotter than the hot water?

[Roly]

I'll agree with Mr_Mike , bad thermal valve along with a convection loop. Can you shut off either the hot or cold water supply next to the pump ? Make sure electric to pump is disconnected. Doing this will stop the convection loop. See if that works. If so replacing the thermal valve will fix it, but if this is the type system that uses the cold water supply as the return the cold water will be warm until cold water forces out the recirculated warm water. Roly