why does the water pressure in my house drop to almost nothing when 2 or more faucets are turned on?

speedball1

How old is your house? What material are your pipes made of. Copper, plastic or galvanized? Did this happen all of a sudden or come on slowly?

Brucem55

House was built in 1974
Copper Pipes
After third bathroom was added problem started.

ballengerb1

I'll bet the third bath was just tapped onto the original piping which was not sized for this many fixtures. Check to see the size of the pipe they tapped into, could be a small line about 3/8" and that is way too small to have two or more rooms on it. Once you track this down Tom can talk you through ways to repipe the third room, if the pipes are exposed in the basement or crawl it won't be too bad.

Brucem55

They tapped into the opriginal piping, but used 1/2 just like the original sizing. This was all inspected by a city engineer and should not be outside those parameters, but i will check with them as well.
The plumbing they tapped into is in the wall on the second floor and i ican get to it, i ijust have to create a door for it for future repairs.
I will double check the plumbing.
Thanks

ballengerb1

If they tapped into a 1/2 " line with another 1/2 " line the flow will be greatly impaired if a faucet or fixture is used in two locations at the same time. Piping is a bit like air ducts that start out large and get progressively smaller as they go downstream. Anytime you tap into the end of the run there will be pressure issues. let us now what you find once you cut your opening. Doubt that a city engineer actaully inspected your job, lucky to get a building inspector.

speedball1

It's not the new size of the 1/2" branches that concern me but the pipes they connected the 1/2" pipes to. If they came off another 1/2" pipe you have located the problem . There should be no more then three fixtures being supplied by a 1/2" branch. Any more fixtures on a 1/2" branch and you began to run into volume and pressure problems if too many are in use at the same time. Both hot and cold branches to the new bathroom group should have been taken off a 3/4" main. Regards, tom

Brucem55

It was a building inspector, my bad.
Speedball1,
i have to go with what your saying, my father was a plumber for 30 years before he died in 1983 and I now remember him saying all bathrooms should have thier own line coming of the main coming into the house.
I can tap in the cold and hot water in the water closet can't i ?