Pressure and flow: Shower trickles when toilet is flushed!

[coalminecanary]

Hey everyone... I'm looking for some general information regarding household water pressure, flow, and how to increase the number of water "outlets" we can use at once. The house is old, but all plumbing appears to have been updated to copper. We have found that the second floor shower flow is okay... not fabulous, but acceptable. However as soon as another tap is turned on, the flow is dismal. It doesn't seem to matter where in the house the second source is opened (laundry, kitchen, flushing a toilet) so I'm worried that the supply line to the house is to blame. I did a rough measurement, and at the kitchen faucet with all other taps closed, I measured about 3 GPM flow. I then realised that the fixture is probably designed to restrict flow so I took another measurement in the basement laundry tub and read about 4.5 GPM (this was all from filling a bucket and timing it).

I don't have a pressure guage, but once it gets a bit warmer and I can turn the outside tap on, I'll measure the pressure there.

I'm just wondering if these flow rates are reasonable? If I want to comfortably run two showers at once, where should I start in troubleshooting the water system? Since the house is older, I am assuming the buried supply line is probably quite old. I don't mind investing some money in a solution, but I don't want to waste thousands replacing the supply line, or replacing internal plumbing only to find I've barked up the wrong tree. I'd also like to do as much troubleshooting as I can on my own before bringing in the pros to do whatever work is beyond the scope of my abilities.

Any tips you can send my way would be much appreciated!

Thanks :-)

[suemarkp]

There are multiples palces where you could have a problem. I'd put on your pressure gauge someplace on the internal piping (outside hose bib is OK, and those gauges are easy to get). Read the static pressure (pressure with no water flowing but spigot opened). This should be in the 40 to 80 PSI range.

Next, turn on your kitchen sink and leave it running when you go read the gauge again.

Now, turn on the laundry tub (with kitchen still running) and go read the gauge.

If the pressure keeps falling significantly as you increase the flow, your pipe to the house is too small or restricted (e.g. corroded galvanized pipe).

Is your water pressure supplied by a city source or a well?

If only certain fixtures caused you shower to get robbed, then I'd suspeect an internal pipe that was restricted. But with new copper and what you described, it sound like it is outside or the transition from outside to inside.

[sloooo]

Might want to take a look at your regulator too. I had the same problem last year. Turned out my regulator had failed on me.

[coalminecanary]

Thanks for the tips (and sorry for the delay.. I have been without my computer for two weeks).

The house is fed from a city source. I have not spoken with the neighbours about their pressure yet since we just moved. The line comes into the house galvanized from what I can tell. Part of the buried line might even be lead. This part of the city is old (house is c.100 years maybe more -- the last deed change on the right-of-way alley was in 1899!)

By regulator, do you mean the water meter? The meter is rather new... probably within the last 5 years. It's an indoor water meter wired electrically to an outdoor sensor. The city required installation of these over the last few years. Too bad the previous owner didn't do a supply line upgrade when he had the meter put in. Oh well!

Our inspector told me that some people replace the line from the main shutoff to the top of the hot water tank with a wider pipe in order to help with household pressure. I personally don't understand the physics behind this solution and it seems to me it's a gimmick. But it's a much easier temporary solution than digging up the main feed... is there any truth to this?

Luckily the house is only about 15 feet from the road so at least there won't be too much to dig :-p

Thanks again!

[AllanJ]

The regulator is a gadget that provides a reduced water pressure in the pipes in your home while an increased pressure is present in the water main.

You can get a feel for where a constriction might be, without a pressure gauge, just by observing the flow at one faucet when you turn on another faucet. You will need to try different combinations.

Are other outlets/faucets besides the shower affected? Are both hot and cold water affected?