Water heater piping


Just replaced my water heater last night.
I used to do some plumbing and have a general knowledge.
On the old water heater, the cold water feed, was 1/2" copper, that narrowed down to 3/8" copper, before entering the 3/4 nipples into the water heater. The hot water coming out, was also 3/8" copper coming off the 3/4" nipple and fed a 1/2" hot water line.
Undersized piping, I'm sure.
I would like to someday, redo the plumbing in the house and take out some of that undersized piping. So, I hooked up the water heater with 3/4" from both the hot and cold, and plumbed into the 1/2" piping (planning for the future).
This morning, while showering for the first time with the new water heater, the water temperature was very inconsistant and the water pressure seemed lower. The water would go from hot to cold and it was very hard to maintain a stead temperature. The water was hot...very hot, when turned to just hot.
At first I thought maybe it was an anti-scald valve or something...that I had the water too hot. But I realized this was not an anti-scald valve. It was a regular oldtime shower valve.
Would my taking that 3/8" pipe out and replacing with 3/4 cause these symtoms? Or could it be something with the new water heater?
Thanks for your anticipated reply.
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snipped-for-privacy@gmail.com wrote:

You did the right thing by going from 3/4" to 1/2" and eliminating the 3/8" pipe. I do not think doing that should affect the inconsistency of the temp or the water pressure in the shower. Try testing another area like the kitchen sink or washing machine and see if the temp and pressure is consistent. If you still have the same problem, you might have a blockage somewhere.
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Keep in mind, that this is what I have now:
<-----Cold water 1/2"------> | | | <---------Hot water - 1/2"------> | | 3/4" 3/4" | | | | | | --------------------------------------------------------- | Hot water heater | | |
So I have 1/2" feeding 3/4 lines as well as 3/4 lines feeing 1/2 inch.
To try to correct the problem, this morning I closed the feed valve just a little, thinking maybe if I reduced the flow, it might help?
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snipped-for-privacy@gmail.com wrote:

No, the 3/4" shouldn't matter. Certainly didn't lower the "pressure" or flow.
You say the water is very hot now. It may simply be that the 'stat on the new heater is set higher or has a wider differential than the old one. That high temp can make the shower control difficult to adjust. Set the tank temp lower as an experiment.
Jim
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Thanks Jim, for the reply.
The problem is, that it will go from hot, to cold, without changing the shower control. I can be standing under the shower perfectly fine....and then get a shot of very hot water, followed by colder water. And this happened consistently this morning.
I'll try experimenting, but I wondered if there was something else??
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snipped-for-privacy@gmail.com wrote:

Gonna take some work to track down.
Let the shower run (or have someone use it) and you feel the pipe temp exiting the heater. See if it varies there.
I'll take your word that the shower control is not scald-gard, etc. But could the internal parts (washers/seals) be reacting to the temp?
Sounds silly, but check that the heater isn't plumbed "backward", i.e., Hot/Cold reversed. Doing so defeats the "dip" tube inside.
Look for possible cross-connections between Hot/Cold. Single handle faucets and washing machine solenoid valves can make a path from Hot to Cold.
Could a toilet tank be refilling (due to small leak) while you are showering?
Jim
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Speedy Jim wrote:

I agree with Speedy. It sounds to me like it is something at the shower, but he has other good ideas as well.
I have had more than one older valve do strange things with washers expanding and contracting.
--
Joseph Meehan

Dia \'s Muire duit
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Maybe the water heater itself is the problem. Bad dip tube? My first gues was that the temp was set too high.
Bob
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For sure & you did the right thing by fixing that.
Your hot water problem could be caused by a missing dip tube inside the hot water heater. When you put the new pipe on the heater, did you heat & solder with it still connected to the cold water side of the heater? If so, that may have melted the small lip on the dip tube that keeps the dip tube in place (inside the cold water inlet nipple). Depending on how close you were to the heater, that is.
Dip tubes cost about $5.
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Just wanted to thank you all for answering.
I had considered the dip tube. But I was careful not to heat either "preinstalled" nipple, with the dip tube attached. The nipples were noted on the instructions as "heat traps". And there was clear instruction not to solder anything near the nipples.
I also considered the shower valves "anti-scalding" feature. I appreciate your bringing that to my attention as well.
But it appears, it was simply set too hot. The old water heater was set VERY hot. I remember now, that it was considerably higher than others I had installed. But I didn't think twice about it and set it the same temp. It was nearly 150 degrees at the tap.
I lowered the temp on the water heater and after a few adjustments all seems well. I suspect, that our main bathroom may have an anti-scald valve. The older shower I was using doesn't have one, but the over heated water must have been warping washers or perhaps plastic valve stems and causing the inconsistency.
All seems well now, except there is slightly less pressure. I wonder if that has to do with the larger pipe size? It's not a problem I eventually plan to re-pipe the water system.
Thanks for your comments and suggestions. Much appreciated!!
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