Water pressure problem

I have an apartment house with one upper and one lower apt. It is probably 70 years old. If only one faucet is turned on in either apartment, the pressure is fine. However, if the lady downstairs is running a faucet, or her washing machine, and I turn on a faucet upstairs, there is a trickle of water. I put a gauge on an outside faucet and it showed 60 psi. I did that and ran upstairs to turn on a faucet and the gauge still showed 40 psi. The faucet was on the opposite side of the house where the main line comes in.

The lady that lives downstairs said that if a faucet is on upstairs and she turns on a faucet, she has no pressure. So it is both apartments. She used to live upstairs before moving downstairs and said that it has always been like that. I didn't realize how bad it was until this past week when I was upstairs painting and cleaning. The tenants that were living upstairs had complained about the water pressure, but were behind a couple months in rent, so I figured they would be gone before I could figure out what to do, and was right. I would really like to get it sorted out before I rent the upstairs.

I was ready to pay to have the line to the main dug up and replaced. A Home Depot plumbing guy suggested the gauge. From what I understand, 60 psi is pretty good.

I thought that maybe the inside pipes may be corroded. But if that were the case, I would think that the pressure would stink all the time, not just when more than one faucet is turned on.

I checked all the valves in the basement to make sure they were fully open. I could not find a regulator near the meter (like my house has). I don't know if that is because it is older(?). I don't see any leaks anywhere.

So, does anyone have any suggestions on what I can do. My plumber said we could replace the pipes that feed the downstairs apartment to see if that would help (before going through the expense of replacing those for the upstairs at the higher cost). I don't know that doing that will help either because, again, I would think that the pressure would be awful even if just one faucet was open.

Any suggestions would be greatly appreciated!!

Thanks!

I'm not a pro, but my thought is one of two things: the main line is probably galvanized and is restricted, and or some of the house lines are galvanized and obstructed. What is the size of the supply from the road? Is the pipe in the house copper? If not, you may be in for a repiping to solve the problem. Pressure when there is no flow and a significant drop when there is a flow is an indication of restrictions. A drop of 20 pounds when a second faucet is opened seems like a lot to me. Ideally, if the flow and the size of the pipes was properly designed, you'd not see much of any drop in pressure.

I don't know the size of the main line into the house. I have a feeling I will be finding out soon... when it is dug up and replaced! Most of the lines in the house are copper. I need to take another look though. But I do know that the line in the basement that comes in from outside is galvanized. It is a couple inches in diameter. It is flaky and rusty on the outside. Maybe the inside is as well - or worse. Any thoughts on whether I should start there? I will check to see how much of the pipes are copper vs. galvanized. Also, the plumber said that there are so many right angles in the piping especially those leading to the upstairs apt. - and said that they may be impeding the flow. Would that make a difference? I bought a "Everything you ever wanted to know about plumbing" book, but haven't gotten that far. Thanks for your help and ideas!

One further thing to check: you said the pressure dropped from 60 to 40 when you turned on a faucet. What if the other apartment also turns on a faucet so that you have the trickle issue? My guess is the pressure measured at the outside drops even further, perhaps below 20. If this is the case, then replacing the pressure regulator valve would fix it.

"too many right angles" sounds to me like somebody reaching for an explanation.

Water Service

Sounds to me like you need to replace the galvanized water service. It closes off inside.

In my limited experience, all those right angles may be a source of pipes banging, but shouldn't affect the pressure (much). The water likes to keep going when you shut off a valve, right angles make it worse - more segments wanting to go in more directions = more chances of it banging into something.

Well, it looks like I will start the process of replacing the galvanized pipes. My plumber is going to break the line where it comes in from outside, attach a gauge, and see what the pressure is like right there. He will start by replacing that pipe. That particular pipe is in pretty bad shape looking at the outside. The inside may be worse. He will find out. All the pipes in the house are galvanized. The only copper are those recently put in for new hot water baseboard heating. It will be a long process so that I can spread the expense over time. What fun!!

Thank you all for your suggestions and information!!