I have 3/4" copper coming in from the street. In the basement I have a 5/8" meter supplying a duplex home. Is there some reason the meter would be undersized? Is it typically possible to have a 3/4" meter installed in this situation to increase capacity, without changing the incoming line.

 

That would normally be up to the water supplier; give them a call. The meter sizing you mention is not uncommon, but 3/4" seems a little lite for a duplex.

 

so 5/8's would be quite a bit light, don't you think? here it's common though. on a parallel note, when I moved in the was a 30 amp service for each apartment. nothing like the good old days.

 

It may be, I'm not conversant with the fluid dynamics. But I often connect 1" or larger water services to 5/8" meters. The meter belongs to the water company & they'll size it as they see fit. If you ask them for a larger meter, they might give you one & they might want some money for it. The pressure and the distance also play a role in the volume you'll get.

 

The city had to replace the 35-yr-old main feed from the street to my meter in No. Cal. after it started leaking, so I asked them why the meter was only 5/8" when their feeder as well as the pipe to the house were larger. They said it served as a flow restrictor to limit the total flow in the city at peak demand periods. As steve_gro said, I could get a bigger one but for a monthly surcharge + install fee.

 

BTW, since my original post I contacted the city. for $40/year I can have a 3/4" meter installed, no other charges. i'll upgrade the old 3/4"galvanized pipe serving the water heaters first, but this seems like a pretty good deal, versus digging things up and putting in a bigger supply line from the street. it's nice when things are designed to be upgradable.

 

$40 a year sounds extremely reasonable.

 

Most water meters are downsized from the pipe size. 3/4" copper is only recommended to about 7 gpm. On the other hand, a 5/8" water meter can flow 20 gpm and a 3/4" is 25 gpm. In order to get 20 gpm out of 3/4" copper, your pressure loss would be 40 psi per 100 feet of pipe and the water hammer would probably damage your pipes. The only gain you'll have by swithing to a larger meter is about 1 psi. To get more volume you'll need a larger line. A 1" line can flow 12 gpm safely. Save your $40!

 

Beerman, Thanks for the guidance on this. I need to follow up, because I'm not sure that your recommendation that I keep the meter at 5/8" matches my situation.

Currently there is a 3/4" flex copper into the house, then a 5/8 meter, then 3/4" galvanized supply pipe. I'm planning on replacing the 3/4 galvinized supply pipe with 1" copper, regardless of the meter change, as I understand this will have a big effect. So the meter change I'm trying to understand is going from:

3/4 service to 5/8" meter to 1" house supply

to:

3/4 service to 3/4" meter to 1" house supply

Given I will increase the main supply pipe size to 1" inside the building - is the difference in the effect of increasing the meter really so small? To my inexperienced eye, this seems like a literal bottleneck, considering the cross section of 3/4 pipe is almost 50% bigger than 5/8. And I'm not sure that comparing the max flows of the meters really address the pressure drop that the different meters will cause. Also, is water hammer an issue for the supply pipe before the meter or should I expect higher capacity for that 3/4" pipe.

Thanks.

 

The length of the pipes is usually the issue. Like the difference of flow you see right at an outside faucet vs at the end of a 100 foot connected to that faucet. The water meter is so short and beefier it can withstand a much higher velocity than a 100 foot service line. The 1" at the house should help somewhat but a 3/4" service can only supply so much water no matter what is at the other end of it. The best bet is a 1" service, 3/4" meter, and 1" into the duplex. Except for the cost.