I recently replaced my hot water heater, basically same capacity, etc. as the previous heater. I am noticing a drop in water pressure in the entire house, guess would be 20-25%. The only change is I used a dielectric union between the new heater and copper pipe.

I have to assume the water heater replacement created the drop in pressure. Is there any way to test if I may have created a constriction in either the hot or cold lines? I assume a constriction would reduce water pressure -- it is consistent throughout the house: kitchen and bathrooms.

Thanks... Tom.

Did you turn Valves all the way back on after replacement?

Remove a aerator and check the screens. Is there trash and debris on them?
Turn the water back on with the aerator removed. Did the pressure increase?
What I think might have happened is that installing your water heater you disturbed minerals built up in the pipe walls and they are now clogging your system. Let me know what you find. Tom

Remove a aerator and check the screens. Is there trash and debris on them?
Turn the water back on with the aerator removed. Did the pressure increase?
What I think might have happened is that installing your water heater you disturbed minerals built up in the pipe walls and they are now clogging your system. Let me know what you find. Tom

No, this isn't the problem. Water pressure is normal for about 3-5 sec, then drops.

Is is possible that you applied heat to the fitting on the cold water inlet of your water heater. There is a plastic dip tube in that fitting that when heated it can deform and possibly slow down the water coming into the heater.

This also can happen if you had plastic lined fittings where the nipples enter the cold and also the hot side of the heater.

Hi Tom...

Did you shut the water off to the entire house when installing the water heater or did you shut the cold water shutoff just to the water heater..

If you shut water off just at the water heater it is almost unheard of that both the hot and COLD water to the entire house would be changed.

If you shut the water off to the entire house then it may be that the main shutoff did not get fully opened, or it could also be a pressure reducing valve has gotten clogged up at the screen and needs to be cleaned... see image below.

Is the entire house really changed or is it just the hot water at the sinks and the tub/shower valves (these have pressure balancing systems that would make a drop in hot water volume look like it was both hot and cold). Let us know more here... O.K.

MARK

Mark,
I read your post. I have the same problem; whole house low pressure, cold and hot. I had turned the water off for the whole house while replacing the gas heater.
I see your picture of the strainer. Where is this located and is it a job for a layman.
Scott

Try turning off the whole house again, then all the way back on?

Strainer is located in the pressure reducing valve (see image at my prior post) and is located at the main water supply by the water meter if present at all... ;)

Try Stratmando's fix first. Otherwise, remove the aerators at the faucets and see if that improves some things!

Mark