flow down to trickle. Why?

a friend showed me his low flow last night. I was amazed how almost NO water flowed in the lav, after the toilet was flushed. It is worse on one side of the house. It was always bad but it got so bad in the last two years that now they take theirs showers in the YMCA gym instead of at home...

Possible causes? Anything to be done? Anything that might improve the pipes' flow, instead of breaking open walls and replacing pipe?

He got the house five years ago; it was built in 1950, the visible pipes in the basement are 3/4" copper entry from the city, a 3/4" copper ballcock valve, a reducer and 1/2" copper from there. There will be a number of elbows in the walls too. Distance run is 50 feet to the two bathrooms on opposite sides of the house. The copper looks new to me, not old. Under the kitchen sink are new looking braided flex supply, and new PVC drains properly designed, and so new they still have bar code labels on them from the store. He has no other information about what might have been done before he got there.

I told him that he has two problems combined: one is that a 1/2" copper pipe (30 feet away from the kitchen and 50 feet from the bathrooms) is barely large enough for a house with two full bathrooms and a fully equipped kitchen.

The other problem is something else making the situation worse, but I have no idea what it is. Something blocking flow, down at the first Tee?

The only change he has done is to install a new shower valve. That side of the house is where the problem seems worse, the flow is lowest. He didn't want to measure flow with a stopwatch and containers, but I might just insist.

David

back flush the lines

either he has galvanized pipe that is
rusting shut.

or he has dip tube breaking up and clogging up
his lines

or he has a solder ball stuck ....

just back flush the lines and see what happens

I guess I'll add my 2 cents here: Did you try to open the house main shutoff all the way? And if it is open all the way, have you tried to disassemble it and check that the internal components are working as they should? Did you check the shutoff at the meter to see if it is open all of the way? Did you take a pressure reading? Did you check the aerators of all faucets and showerheads?

You say the potable system appears to be copper to you, and the drainage has been somewhat if not totally replaced with pvc, so I wonder if there is some prv valve or something like that needs maintenance. A 3/4 run from the city seems like there should be enough flow/pressure to serve the house, atleast better than the conditions you are describing.

Backflush'n see what pops out. That is good to do.

i'll get him to ask neighbors if their houses (built at same time) ever had any galvanized pipe. The bathrooms, kitchen and basement show no trace of it.

assuming ballcock is open, and aerators are not all bad, then it does seem like an object is blocking flow, far down, at the first Tee or at the ballcock valve at entry.

his cold water is as bad as the hot, so I guess I don't need to check dip tube.
There is no PRV.

david

See this sometimes when houses are remodeled, and every inch of plumbing inside the home is new, but the line from the main is still galvanized.

I checked one that had 90 PSI at 2 GPM. Might require some digging to get the whole story.