Low water pressure when using hot water with multiple things in use

[Orangepeel]

So the condition was present before you replaced the old heater with new........so the issue is not with the heater. It is a tank type correct?

If it is a tankless, there is your answer......it is the tankless.....

Hot side piping and hot sides of faucets and shower valves and such are more subject to corrosion, and mineral buildup over time. I am guessing you have galvanized piping somewhere? If not, it is a piping issue having more to do with size.

It's a tank. All the lines in the home are copper
If it's a size issue would you redo them with bigger lines to solve the issue?

 

[burbguy82]

It's a tank. All the lines in the home are copper
If it's a size issue would you redo them with bigger lines to solve the issue?

Is the issue with flow ONLY when multiple fixtures are on?

What is the size of the pipe on the hot side of the heater?

 

[Orangepeel]

Is the issue with flow ONLY when multiple fixtures are on?

What is the size of the pipe on the hot side of the heater?

1/2 inch I believe

 

[burbguy82]

1/2 inch I believe

Depending on incoming water pressure, and distance, I think that is your issue judjing by what you have said......... But 1\2 copper, flows the same or close to 3\4 pex, all variables being equal.

You would only have to increase the size to 3\4, a partial distance, but that distance is hard to determine over an online conversation. Without knowledge of plumbing and its installation, you might want to consult a local plumber.

If you can take some detailed pictures, and provided that a lot of the plumbing is accessible, I can help you do it, but you have to be able to perform plumbing related tasks.

 

[Nukeman7]

How long have you live there? Point of question is: do you have anything to compare it to? You mentioned a new water heater. Was this condition present before the heater was new?

So the condition was present before you replaced the old heater with new........so the issue is not with the heater. It is a tank type correct?

I don't see where the OP has clearly answered this critical question.

If the condition manifested only after installation of the new A.O. Smith water heater, it is not a piping/fixture issue. If it was occurring prior to installing the new water heater, it is not a problem with the new A.O. Smith unit.

 

[Orangepeel]

I don't see where the OP has clearly answered this critical question.

If the condition manifested only after installation of the new A.O. Smith water heater, it is not a piping/fixture issue. If it was occurring prior to installing the new water heater, it is not a problem with the new A.O. Smith unit.

I did answer but it probably got missed. Yes the issue was there before. I actually am redoing the lines and installing an expansion tank this evening. Hopefully it solves it.

 

[oilcandave]

Look for a globe valve installed backwards on the hot side...the washer screw will loosen and release the washer or close to it up against the seat restricting flow on the hot side. In 50 years of home service i have found this at least 15 times...

 

[Sumboodie]

With the water running in the house, I would adjust the pressure regulator up to 80psi and see if that helps. You need to adjust with water running to get a "dynamic" pressure reading, rather than static. But sometimes the pipes are simply undersized or going bad and a repipe is the only fix. I'm in a 1946 house and simply live with it.

Good way to blow old pipes apart. 40-50 psi is plenty high for a house.