Hi All.
When my cold water is heated up in the tank and it reaches the required temperature the hot water pressure is next to nothing more than a dribble when trying to fill a bath. After heating the water if I turn the heater off for a while the hot water pressure is very good.
Any ideas to solve this would be gratefully appreciated.

Hi Crouchy... what kind of tank? Gas or electric? How old is the tank?

Is everything OK at all the other fixtures?

What type of tub/shower valve... how many handles associated with it and do you pull up on the spout to divert water to the shower or is there a separate control for the shower and if so, how is the pressure/volume from the shower??

Please answer all questions, OK?

Mark

Hi it's a copper water tank heated by an electric element. Probably original tank from when house was built 1972.. I have been here 14 yrs and always had this problem. The Shower is separate running off cold water mains so pressure is good. Hope this helps.

Hi crouchy. Never heard of a copper water tank. I think at this point, without some pictures and a lot more info, it is time to call in a plumber. Sounds like you have a unique system.

MGD, think UK. Crouchy, is this a gravity fed system from your attic or something else?

I would say gravity fed. Thanks

Right you are ballengerb. I have enough problems trying to keep up with what's happening here, so I think Ill leave the UK up to you guys, lol.

MGD, I can recognize a UK system but am better off not blindly trying to help further. I can wait for Mark or Milo

Hi Guys...

I'm not much better with the stuff in the UK, but as far as I can figure, the only way to resolve the issue raised by Crouchy is to start disassembling things...

First, I would check that the cold water shutoff going into the copper tank is wide open.

Then, I would check pressure at a drain cock, if present, at the tank... see how pressure is there.

Then I would disassemble the tub valve and purge/clear the pipes of debris/sediment. I would check volume at this time by putting a towel over the valve and turning hot water on full flow... this should tell Crouchy tons, here.

If all that didn't tell Crouchy what was happening, I would see if there were any shutoffs in the hot water line and I would disassemble them to see if a washer has gotten dislodged... would explain the changes in pressure seen.

Next, If nothing was obvious at that point I would probably change out the cold water shutoff into the water heater, check the nipples at the cold inlet and hot outlet to see if these are clogged (especially if "heat trap" nipples)and change these if needed, too!

Finally, if there is galvanized pipes in place I would check to see just how choked down they may be and if needed, I'd start to replace some pipes.

That's my thoughts... :)

Have a great day guys!

Mark

PS: We still have tons of old copper water heaters in the Boston, MA area...darn things were built to last.