low hot water pressure.
I own a two family home. About two months ago we moved from upstairs to downstairs. The new tenant is complaining that the hot water pressure is low. There is an old washer hookup in the basement on the upstairs line from before the upstairs had a washer in the unit and that line has very good pressure. The only thing other than not use the water up there for about three months I've done was install a shutoff valve. If memory serves I cooked it a little. It turns a little hard. It has this little bleeder knob on it. I would just replace the valve, but pressure downstairs is very good.
I'm pretty sure I know what you mean when you say the "pressure is low", but it's likely not low pressure, it's low flow. Lots of folks confuse the two, so don't feel too bad. I would venture a guess that the valve got too hot and is not opening completely.
I'm not positive. But I replaced the valve and no diff. I'm pretty sure it is a case of sediment buildup on the filters on all fixtures. I cleaned the faucet and it works as it should. I now have to do the rest.