low Cold water pressure

[21blackswan]

my mother is having low water pressure in just some of her cold water lines [hot lines are fine]

I'm pretty sure it's not the shut off valves, underneath

any other possibilities?

thanks marc

[dpb]

...

Galvanized by any chance? If so could be internal rust buildup obstruction.

Alternatively, it's _possible_ altho somewhat unlikely that there's a PRV in a location downstream of a branch from the main feed. More likely if there's been an addition or other modifications since original but in old work, who knows what might have been done?

[21blackswan]

yes, it could be galvanized i suppose. Sounds like a real possibility, i hadn't thought of

the house is about 25 years old, in Southern Calif. What are the chances it's galvanized?

thanks marc

[BenignBodger]

At 25 years, the chance of galvanized is pretty much zero. Is the cold water pressure low everywhere or is it localized? Can you follow the path of the water line from outlet-to-outlet? Frequently an outside hose bib will be first in line. If the problem is localized, are you sure that there isn't a water filter inline? I have lower flow in my kitchen's cold side because I have a sediment/chlorine filter inline to improve my coffee's flavor; if the filter was to be ignored for a long time it would definitely cause problems. Alternatively, there could be junk in the line or in a valve or in an aerator or a pipe could actually be crimped if there has been work on the home recently.

[nestork]

The chances are slim to non-existant that a house vintage 1987 will have been built with galvanized steel water supply piping. By 1987, copper water supply piping was standard through the US and Canada.

Normally, when you hear complaints about low water pressure at certain faucets, the problem is that something is clogging the aerators in those faucets. The aerator screws on to the end of the faucet spout, and it's what makes the water come out as lots and lots of drops rather than a continuous stream of water like you get out of your bathtub spout. That's because the aerator makes the water flow through a screen which breaks the flow up into gazillions of droplets. It's the screen that typically gets clogged up.

The problem is, if the aerator is clogged, it'll be equally clogged for both hot and cold water.

I would ask your mom for more info. Which faucets have low pressure? And, are all the low pressure cold faucets equally low in pressure? Are they single handle faucets or two handle faucets. If two handle faucets, do they have separate spouts as well, and do those spouts have aerators on them?

Normally, low water pressure complaints arise immediately after someone has a water heater replaced because the shaking and jarring of the piping knocks stuff on the inside of the pipes loose, and that stuff ends up clogging up faucet aerators giving the IMPRESSION that the water pressure in that faucet is lower than the other faucets.

Most faucet aerators also have flow restriction devices in them. Those flow restictors will have small holes the water has to flow through, and those flow restrictors will get clogged up with stuff too.

The aerators will unscrew from the end of the spout by turning them counter clockwise, just like a light bulb.

[dadiOH]

Pressure is going to be the same everywhere, flow may not be. Therefore, it is a problem associated with the particular outlet(s) that have low flow.

The most likely culprit is - as others have said - the aerator but that would affect both hot and cold, assuming a single faucet. If it is single faucet I'd be looking at the cold water feed between shutoff and faucet as the first place to check.

[Stormin Mormon]

We need a bunch more info, for trouble shooting.

Might try turn off the shutoffs, and turn them back on. Sometimes they get a big of sediment.

[Ed Pawlowski]

Perhaps there is a filter in the cold water line? One that has been there for a long time and never changed?

[dpb]

Again, though, to have the OPs symptoms it would have to be somewhere other than the main.

And, just to point it out from earlier in the thread, the downstream pressure for the outlet flow after an obstruction isn't the same as the static pressure; it will be lower if there is such an obstruction.

When shut off the faucet it will again equalize, sure, and will start at that when opened, but if the obstruction is large enough to significantly reduce flow, the pressure will be lower as well...

Again, the ideas of filters, PRVs or other ideas is worth checking as mentioned.

OP thinks it's not the cutoffs at the individual sinks, but I'd not be quite so certain w/o checking altho again that it's multiple locations apparently and that it is only cold implies something in the distribution in a branch line. Hmmm....wonder if by any chance't there's exposed copper in a basement and somehow somebody managed to partially crush one while moving a large, heavy object or somesuch???

[DerbyDad03]

But don't open it fully and leave it that way, unless it's a ball valve. If it's a gate valve (the type with a round or oval handle that you turn) you should open it all the way and then close it about 1/8 of a turn. This gives you some play in both directions if the shutoff should freeze up from not being used.

I had to close the shut off for the hose spigot at my dad's house this weekend and it was fully open against the stop. It was very stiff from not being turned off in many years and it took some effort to get it moving. I was really surprised that it didn't start leaking around the packing nut, something that often happens when a shutoff is used for the first time after many years, especially if it takes some force to get is closed.