I have an oil furnace with an expansion tank. While having some work done on the furnace, the repair person noticed the flow of the hot water. He said he cleaned something which only took him a few minutes and we had great hot water pressure. Of course it has happened again and trying to work this myself, I see no place he could have "cleaned". I have checked the pressure at well side and seems good and cold water is great and always had been. Any idea?? Could the expansion tank psi have anything to do with this.. Its 12-14psi. Thank you for any help.

It should be about 12 psi cold and 18 psi hot. So... What is it now?

The psi was in that range that you stated.

It sounds fine to me. I'm guessing he cleaned the screen in the pressure reducing valve.

That I am not sure. I looked up some info and can that be pulled apart? The well psi and cold water are really good.

OK, you are talking about your domestic hot water, not the boiler water pressure, two completely unrelated things. Check the valve on top of your water heater, make sure it is fully opened. How old is the house? Is the water pressure on the hot side low at all fixtures?

Is this one of those systems that has a coil for hot water taps in the boiler? If the guy found and cleaned something, you should be able to too.

The furnace was in stalled around '91 and the entire house was pretty much redone. At that time they added a secound floor and redid everything else. I bought the house last May. There is no water heater and the hot water is poor, at all fixtures. Thanks for the continued help

It is possible some crud has found its way to each water tap. Pick one, shut the water off to it. Pry off the cap, remove the screw under it, remove the handle to reveal a nut. Unscrew it and remove the whole works. This may be a job for 2. Hold a towel over the open tap, and crack the water open. If it gushes out, pushing some crud out, you have found and fixed the problem. Sometimes the cartridge you unscrew is plugged up inside and must be replaced. Repeat at the rest of the taps.

Otherwise it is back to looking for something to clean at the boiler. There are filters that look like a ''Y'' except the one branch doesn't go anywhere. If you see one, shut the water off and unscrew the plug from the plugged branch. If you find a crudded up screen, aha, clean it.

Ok. All the fixtures have the problem. I didn't pull them all apart, but did remove and cleaned the little screens in the facut. Now the pressure comes on strong for a secound but slows right away. I don't have any "y" cartridge or anything like that... I do see on the back of the furnace, near when the psi blow off for the boiler is a faucet like valve. I would guess that would be to drain the boiler.

If the screens were dirty and cleaning them gave a little help, that is a sign of dirt elsewhere. I still think if the service man found and cleaned something near the furnace, you should be able to also. Maybe call him back and watch him this time.

It is also possible all the taps have crud in them. As I said, check one as a test. Once you check one, you will have a much better idea of whether you should do the rest.