Dear Ask Me, I want to increase water flow when multiple fixtures are running. We have a 2900 sq foot two level L-shaped rancher built in 1963 in Atlanta. For our family of four, the water pressure is fine. When someone is taking a shower there is a noticeable drop in pressure and volume when another fixture is opened. We frequently host house guests and are unable to run two showers and another fixture, e.g. the washer machine, at the same time. The supply from the street is about 100 foot via non-copper, grey metal pipe. The OD is about 1". This comes inside and connects to 3/4" copper, passes through new PRV and new expansion tank with new ball valve main shut off. Main runs are 3/4" copper. The showers are out about 70 and 100 feet off of 3/4" copper. When I hook up a pressure valve to an outside hose spigot (1/2" line 5 feet off 3/4' line) it reads 60 psi. When I open one tub full, it drops 20 and reads 40 psi. When I open two tubs it drops 40 and reads 20 psi. When I open just one shower, the way we like it (tub near full open, but when shower engaged, the flow is cut quite a bit but with good pressure and volume), the presure drops 10 to 50 psi. When I run two showers, pressure drops 20 to 40 psi (this is not quite enough pressure and volume coming out of the shower). If another fixture is turned on, the pressure drops below 40, and pressure seems inadequate all around. If I turn the PRV up to 75, curiously the drops increase and the final pressure readings are the same as if I had the PRV regulated to 60 psi. So, turning up the PRV to 75 does not solve the problem (also at 75, the pipes rattle when I turn off the water to the shower--no problem at 60 psi). I did not try to turn the PRV above 75 psi but there was substantial thread remaining to try to do so. The valve at the street (city water) is fully open and sits at an altitude of 800 feet above sea level, although I do not know the drop or climb to our house--we sit at a relative high point compared within the neighborhood). There is no movement of the street needle when all house fixtures are off (ie no external leak). The main ball valve is new and fully open. I did not think copper corrods. I have old shower heads, but they seem to deliver good volume and pressure when run alone. If I can get this pressure issue addressed, so I can run multiple fixtures with adequate volume and pressure for when I have guests, I will address the hot water part of the equation with two 185K BTU tankless water heaters (there is a convenient "T" in our "L"-shaped house which separates three showers/baths and sinks from the kitchen, dishwasher, and washer machine). We do not have an irrigation system (and will not be getting one). What are your thoughts? Thanks, Michael

''about 100 foot via non-copper, grey metal pipe. The OD is about 1"'' Sounds to me like 3/4'' galvanized pipe. It may be corroded or limed up restricting the flow. Ripping it out and replacing it with copper or plastic would be expensive. Might be a landscaping disaster too.

You could install a large pressure tank in the house, perhaps more than one near points of heavy usage. You wouldn't need any controls, just tee it in. When the pressure drops because you are using water, the water would flow out of it. When the pressure goes up after shutting the water off, water would continue to run into the house until the pressures equalized.

See if Tom has any better ideas.

Good morning Michael and Happy New Year,
Has your water pressure ever been satisfactory or has this been a ongoing problem from the start?
Your local, State and National Plumbing Codes address this problem when they mandate no more then three fixtures tied on a 1/2" branch off a 3/4" main.
I think Labman put his finger directly on the cause of your problem when he zeroed in on the galvanized pipe house supply from the street.
I have seen 3/4" galvanized pipe choked down to a opening the size of a lead pencil by mineral build up over the years.
You simply don't have the volume to support running multiple fixtures at the same time.
Replace the feed from the meter with 3/4" PVC and I think your problem will be solved. Regards, Tom

Thinking some more about this. In Atlanta, the water line doesn't have to go down half way to China. Rent a trencher, go beside where you think the line is, detouring around trees and shrubs. Just don't get carried away with elbows. For overkill, for very little more 1'' PCV will carry 4 times as much water with the same pressure. Also have locate find gas, electric, etc. before digging.

Dear Labman and Speedball. Cool handles. Happy New Year, thanks for yor advice. I was confused for a second, because I just returned from Xi'An China. But you are right, no need for the pipe to go there. To answer your follow-up question, the situation has been roughly the same for the last six years that we have lived in the now 41-year old house. The main electric line is 20 feet in the air, and the gas line is parallel to the water line but about 100 feet laterally (it was well marked when I bought the house and is aligned with the gas entrance regulator--so, no problem). So I go with 1 inch PVC. Is all PVC the same? How long can I get it, or is it OK to make splices? Is there a tool I can buy to turn off the main valve at the street. Previously, I have tried turning it with a large crescent wrench conneted to a pipe and it would not budge. How deep to bury the line? Is there likely to be a code for the depth (I can check). Fortunately, it is across a relatively level line of grass. Right before the house it will need to go under a standard walkway perpendicualary for a distance of about 30 inches. The foundation is accessible and is standard block. Assuming I do all of this, re-read my supply demands. Will the internal 3/4 inch internal feeds be adequate? What forum should I use to ask gas line questions? Best regards, Michael

Hi Michael,

As Labman sez, 1" Pvc is overkill. You will have more volume with 1" but I question if you'll need it. Hey! Your choice!
In my area and on the West coast of Florida we run the house supply in 3/4" schedule 40 PVC. We use 1" on multi-condos and commercial jobs.
3/4" is easier to work with and it will make a long bend without fittings if you need to line it up with the house connection. Schedual 40 PVC is rigid and comes in 20' lengths. There is a built in coupling on one end for ease of installing. Your depth should be the same as your old line To turn off the meter the city uses a "street key" call the city to shut off the meter. Once they loosen it up, a large crescent wrench with a screwdriver for leverage should be able to turn it back on. Don't forget to prime both coupling and pipe with PVC Primer before gluing. You'll have leaks if you don't.
To get under the 30" sidewalk you can tunnel or if you don't like to dig you can jet the PVC under it. If you're not familiar with the procedure just ask and I'll walk you through the process. What problem do you have with your gas line? Ask it here and we'll try to answer you. As for your house piping 3/4" mains are normal, branching off into 1/2" supplies to the various fixtures. This will give you good service unless you tie more then three fixtures on a 1/2" branch and attempt to use them all at once. Cheers, Tom

Thanks for the information. I am getting a better understanding of what is going on and this is leading to me "seeing more data." Supplemented by a little reading, I understand the basis for your explanation of the 3/4 inch main and 1/2 inch branches to 3 or less fixtures. I am now trying to figure out how long the 1/2 inch branches are and how many fixtures are connected per 3/4 inch main. In the meantime, more data: the water meter sits at the street underground, about 100 feet from the house. It is 24 inches deep, which after checking with a few locals is code. Curiously, the street-side pipe into the meter is 3/4 inch OD (not ID) and not copper. Then there is a connector to a short, 3 inch long pipe that is 1 inch OD, looks galvanized, then the meter; I cannot see the pipe leading out of the meter without a little digging. As I said before, it enters the house as 1 inch not-copper, probably galvanized. How can the pipe from the street be even smaller? Could that be the restriction also? Or does it work like gas, in that there is a higher street side pressure. Sorry to complicate matters, but the water meter box is a cast iron rectangular box that has an open bottom. On the street end, and on the on the downhill side, there is a 3.5 inch round hole in the dirt, straight down, that took 3 "gallons" of gravel to fill. There is no obvious water. My neighbor thinks this is due to run off down the hill and into the grating with no where to go, so it made this hole. I also notice that uphill to the box, my driveway has a 3 foot swath of concrete than does not match the old driveway closer to the house (a sign may be soneone dug before we moved in). This raises the possibility that there is a leak on the street side of the meter? I went to neighbor's house; his house was built only 25 years ago (compared to mine at 41). His resting pressure is also 60 psi and his drops are the same as mine, but he has much better maintained flow than I do. I will start a new thread for the gas questions. Thanks, Michael

I don't like that short length of smaller pipe, but wouldn't worry about an external leak. Count on the city being out there to fix a leak big enough to affect your water pressure before it undermined the street. Pressure drop due to pipe size varies drastically. Calculating it requires amassing a chunk of data including the actual volume of water you are using. For comparison, pressure, volume, and length of pipe all are linear, you only multiply or divide by each one once. Some people make the mistake of thinking flow depends on area, half as big of a pipe carries 1/4 the water. Well that is a start. Actually it is not the square, but the 4'th or 5'th power, a 1/16 or a 1/32 as much out of half as big of a pipe. That little short length of pipe could be reducing your flow. Getting the city to change it could be tough.

By the way, my name comes from my primary net presence as a dog expert, Labrador Retriever.