Low Pressure or Flow in OId House when multiple taps used

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Paul Kirby

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Columbia, SC
I apologize if I am posting this incorrectly... I was trying to create a new post and it popped up some other similar previous forums. Several photos below.

I have an old rental house that my son is living in with his college roommates. Old 2 story house built in the 1930's with a wide range of repairs, additions, bubble gum & bailing wire, etc... from the current and previous owners. The house has terrible pressure (or flow?) when two devices are turned on at the same time. It is City Water and we asked it to be checked and was told it was fine. I bought a screw on pressure gauge and attached it to the outdoor spigot - it read 65.
It has an outdoor gas water heater. There is a wide mix of galvanized pipes with old cpvc with some copper etc..
No pressure tank that I can see. I am guessing from what I have read in this great forum - that we should consider the old galvanized piping to be the culprit due to clogging or inner deterioration. My ignorance is around the fact that I would have thought a tighter diameter might actually increase the flow rate (like placing your thumb on end of garden hose). So, I mistakenly thought about this wrong.

My question is - being a rental house with a landlord unwilling to pay a dime for this pressure inconvenience (can't use both showers at same time, can't do laundry while showering, can't use the dishwasher and have any flow out of the 3 other sinks (kitchen and 2 bath), etc.... ). So, what can I do to check to make sure what the issue is? I guess I should have my son confirm this happens with both hot and cold water supplies. Or should we check the valves on exterior hot water heater? I am sure it has not been flushed or checked etc... I am afraid the answer will be the old galvanized lines need replacing... seems like they are primarily the main trunk lines. Looks like all the branches at the bathrooms, kitchen and washing machine have been changed out years ago for yellow/tan pvc lines it appears. And some are copper.

Long enough explanation, Sorry. Will attach photos too ... some of the lines you will see are abandoned in place and at least one pic is of the bathroom addition that had to be rebuilt - walls, floors, ceiling and new shower... but you can at least see the old lines that were still used with this renovation.

Great Forum! Really helpful



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I would see how much the outdoor water pressure drops when you turn on a shower. You will want to have a helper to turn on the shower, or you could turn on the shower, and go look at the gauge. Or take a movie of the gauge.

I would see how much the water pressure at the WH drain drops when you turn on a shower.

You could take another measurement at the laundry taps.

Anyway, the info can help you deduce where the drop is.

For example, if there is not much drop outside, but a lot of drop at the WH, look for a cartridge filter that is in the path, and may have a partially clogged cartridge.

Flushing the WH is more about getting rid of accumulated crud. Blow out several gallons from the drain while the pressure is on. You might want to watch what comes out. Maybe take a movie.


Licensed plumbing contractor
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San Francisco Bay Area
The piping diagnosis is terminal. Sorry.
Primarily, the galv. water pipe is useless, worthless, occluded, obsolete and is not worth going down the path of trying to fix.
Rust particles are not worth trying to track down because there are infinitely more coming.
Hey, wait a minute.

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