Where's the heat!

[Burf21]

So came time to replace the water heater.not even a deal, I've done this a few times tho I'm not a plumber by trade, my profession (C27,landscape contractor) at least provides my with a better than average knowledge of hydraulic systems.The two story home at which this R&R occurred I should say belongs to my 88 year old father in law , not really a DIY guy and a bit short on details as to the repair history of the home. Everything went as planned no issues until, after given time to heat the water I began to make hot water calls on the various fixtures. The very best I could produce was Luke warm water and the furthest being the kitchen sink never achieved that or maybe somewhere between lukewarm and cold. OK WTF now!
History: while my family and I weren't living there at the time, six years ago he had the now failed water heater replaced with the exact same issues. His recollection of its resolve is more than a bit fuzzy but my recollection of it involved, for example , doing things like turning on the ... cold water in the bathroom sink then the shower if you wanted a hot shower. So in an attempt to call hot water to the shower last night I did the same.the result mild lukewarm with periodic moments of slight improvement. I doubled down with reaching out of the shower and flushing the toilet... not bad,it was very close to normal. although I think in the past it may have scorched me.
My understanding according to my father in law is that over time the lukewarm water resolved itself over time. Resolved itself with no action taken by anyone, despite the deep thinking, brilliant minds assembled from "plumbing guys" he knew ,real licensed plumbers and the dude down the street. To me, it seems like somehow in someway the hot water is simply overpowered by the cold.so this is where I'm at. I will say as I've probed around the home and minds of those who should know, it seems the house was re-plumbed at one time and as I look at the service line where it enters the home or at one time did (oddly re-routed) there is a cap off 1inch copper line sticking out of the house about 4 or 5 inches above grade. Obviously the old service line but why not cut it off flush with the house? why the cap?the only thing I cat think is that mr.re-pip out of laziness or stupidity created a "dead leg" which is somehow caused the current situation of no hot water. Help Help Help me please if you can.
Note: yes I did confirm the hot water heater is operating correctly (water is ripping hot)leaving the unit as well as the utility sink 4 feet away. HELP!

 

[Reach4]

"My understanding according to my father in law is that over time the lukewarm water resolved itself over time. "
But then the problem came back.

I was going to suggest closing the available stop valves at each fixture to prevent crossover. See if hot water got to where it was going then. Close the valve for either the hot or cold for each thing piped with hot and cold, including the washing machine and laundry tub. Dishwashers and toilets are not piped with both, so they cannot be the problem.

If yes, you then have good hot water at the far end, start opening stop valves until a problem is detected.

Your dead leg theory about a dead leg causing hot water to not get to the shower holds no water IMO. The worry about dead legs is that bacteria could be growing in there.

 

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[WorthFlorida]

Is there a touchless kitchen faucet? Another suspect a tub/shower.

 

[Burf21]

"My understanding according to my father in law is that over time the lukewarm water resolved itself over time. "
But then the problem came back.

I was going to suggest closing the available stop valves at each fixture to prevent crossover. See if hot water got to where it was going then. Close the valve for either the hot or cold for each thing piped with hot and cold, including the washing machine and laundry tub. Dishwashers and toilets are not piped with both, so they cannot be the problem.

If yes, you then have good hot water at the far end, start opening stop valves until a problem is detected.

Your dead leg theory about a dead leg causing hot water to not get to the shower holds no water IMO. The worry about dead legs is that bacteria could be growing in there.

So grateful for your response and I shall give that a shot. My comment as to the "deadleg" was perhaps the wrong term for what I was trying to explain.
So the 1" stub of capped off copper sticking out of the house I'm assuming was the the old route that the main took into the house when it was built. Post construction someone got the idea to ad a "softwater" system for indoor water use. In this case instead of 90• up and 90° into the house they routed it over 15 or 20 feet,up and into the garage then into softwater filter(subsequently removed sometime later...just for the record)and on to waterheater and so on the the various fixtures.point being , had they left the original service line connected when they added the softwater thing they would have created a loop of sorts.my convoluted idea being, the "deadleg" is somehow causing some sort of siphon or pressure differential or ? I don't know what a portal to another world... causing the cold water problems.as I think about it just seems odd that the only way to get hot water is to turn on the cold supply on any nearby fixtures ( the more the better)
Now for what it's worth I'll ad these facts the the mix for consideration
1.There is a pressure regulator pre house supply, replaced a year and half ago.
2.Where the water softwater was, a brilliant mind made the decision to not sweat the two pipes together or what the heck , union together the mess.oh no, why he got him a flex-line an-a ball valve.yep he made a cute little loop out a what he had.
3.Finally, for now anyway, cold water coming into waterheater of course has a flex ball valve combo but for whatever reason hot line out has one too.
As I said the above info provided just incase it matters and also just to give a peak in to the crative minds behind this mystery. Agin Im humbly grateful for all help.

 

[Reach4]

#2 Using the connector line could have been to make it easier to possibly put in a new softener in the future.

 

[Fitter30]

First thing is to cap off or install a valve in the cold water line after the water heater. By running just the hot water can find out if the hw is running to every fixture and opening cold water valves for hw. How old is the house? Good possibility a section of hw piping to inspect it for mineral blockage.

 

[GReynolds929]

Turn off the cold inlet valve to the water heater. In the house open a hot faucet. Water should stop flowing within a minute or two. If water keeps flowing you have cold crossover somewhere. Leave the faucet open and shot off the cold stop at each fixture until flow stops.

 

[Burf21]

#2 Using the connector line could have been to make it easier to possibly put in a new softener in the future.

For sure but why not remove it with the waterheater.

 

[Reach4]

For sure but why not remove it with the waterheater.

How do you relate the softener to the water heater? Having one can reduce deposits into a WH. Having a water softener loop is a feature for a house to facilitate installing a softener in the future.

A loop is not a dead leg.

 

[WorthFlorida]

Is there a touchless faucet anyway?

Read post 60&61 of the following. I had the culprit figured on post 2
but it took 58 more post to get the problem solved.

Hot Water Coming Out Cold Water Throughout House??

Thanks everyone. Check valves on the cold water supply to the electronic faucets have solved the problem. I think my first post stated that I do not trust the electronic faucets. I'm it's solved and giving us an update. You have to eliminate and then isolate. Have you turned off the pump and...

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