? Max flow out of a 5/8' water meter?

d_millerMay 28, 2009

How much water can I get to my house from a water meter that is referred to as 5/8" meter?

The water pressure at the meter is 61 PSI. So, how many GPM can I get out the other end and still maintain enough pressure of (letÂs say 20 PSI) to operate lawn sprinklers?

In other words, how limited is the water supply to my house by the fact that I have a 5/8" water meter?

IÂm asking all this because I am taking bids from plumbers to repipe my house. Some have suggested that I oversize the plumbing network in my house to get more pressure/flow. Of course, oversizing, with copper, is more expensive. I thus wonder how much more water flow can I ultimately get by oversizing, when my water bill says I have a 5/8" water meter ?

A related question is: does a 5/8" water meter usually imply that the cityÂs water pipe to my house is also just 5/8" ?! The city seems to want to charge around $2,000 to change the water meter ?!

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I suggest you google irrigation tutorials to finely hone your question and be able to make your own interpretations.
Be careful conflating pressure/flow. I could cut you in half with 2500PSI requiring less than a teaspoon of water.
A 5gal. bucket at atmospheric will amply rinse a bather.
A typical max GPM for that size meter,15. The supply line could be anything 3/4" up, probably no more than 1&1/4".

Taking bids from plumbers is always entertaining.Is copper mandated in your area? CPVC is a cheaper (cost wise) material NOT subject to as great thermal loss/gain, acidic water, chlorine from municipal treatment or water hammer effects. If you are satisfied with your present house plumbing, teeing off a larger line could solve your perceived sprinkler problem.

    Bookmark   May 29, 2009 at 12:42AM
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I would go with PEX before I would use CPVC. Much easier to install. You pull and fish it like electrical cable.

    Bookmark   May 29, 2009 at 9:25AM
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Outdoor, before my rusty galvanized main ¾" pipe enters the house I only get 7GPM, HOWEVER that is also from a hose bib which is probably not a full flow valve.
At the hose bib in my back yard (after the water runs through the rusty pipes underneath the house) I only get 5 GPM. That is why I cannot even run a 3 sprinkler head circuit (the watering radious is an anemic 5Â !!?).

I know that my pipes are old corroded galvanized, they need to be replaced anyway and are probably the main source of my water flow-pressure issues. But that, precisely, makes me also wonder whether the cityÂs ¾" (or whatever diameter it is) supply line, is perhaps also galvanized and also corroded, since they are from the same late Â50s era. As a prelude to this repiping project I am considering just replacing the main line to my house first. That will give me a chance to disonnect my main line and measure how many GPM I get using a bucket and timer RIGHT OUT OF THE METER. But what if I, say, get only 8 GPM at the meter? Do I go to the city and say my water supply is inadeguate because of old meter/rusty city pipes?

I am aware of the complementary relationship between pressure and flow. If I can get even 10 GPM and still maintain 20 PSI that would be adequate for my sprinkler system which has 4 circuits with 3 sprinkler heads each (no more than 7 GPM per circuit @20PSI - per sprinkler head specs).

In any case, since I will start this replumbing project by first replacing the main line from the meter to the house, does using 1" copper as a main seem adeguate under the circumstances?

    Bookmark   May 30, 2009 at 3:43AM
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You won't get a representation of what GPM is available through a hose bibb, but old galvanized pipe isn't helping either. Good luck arguing with city hall, although deep pockets solve many problems.
If allowed in your area, I would run the main in PE. Metal of any sort ( barring 300 series stainless) underground is trouble unless wrapped in approved material and maintained. PE goes in and done.
I suggested CPVC in the house because it has a proven record. It can be direct buried. PEX has some claims pending, may turn out fine, just have to see. Copper is long established but sure has some problems, not just acidic water.
Something to consider in your situation (if indeed you have delivery below needs),is a cistern or tankage and seperate pump to make flow/pressure at the volume required. Accumulation can occur after domestic usage, say timed during the wee hours.

    Bookmark   May 30, 2009 at 5:22AM
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The max flow through a 5/8" meter is 15 gpm, at 15 gpm the pressure loss is 8.3 psi. The meter is not the biggest issue. I would say your main is also limited, if your only getting 7 gpm at 61 psi, even through a hose bib.

One inch copper or PE would be fine, you could get ~12 gpm with safe velocities and limited pressure loss.

    Bookmark   May 30, 2009 at 8:37AM
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I measured the flow right out of the water meter and filled a 5 gallon bucket in 15 sec. So seems like IÂm getting ~20 GPM !! at the 5/8 meter with 63 PSI static pressure.

Now, IÂm not really sure if my meter is 5/8". That is what my water bill says and I assume itÂs correct. However, the short brass tab right out of the meter is 3/4".

So I'm optimistic that it will be easy to get 10 GPM at the sprinklers if I run a 1" line to the sprinklers (once I replace/upgrade my service line to 1" also).

BTW. If I have:
- static pressure of 63 PSI (63 PSI at 0 GPM flow)
- 20 GPM at 0 PSI (right out of the meter, full throttle)

doesn't this roughly mean that at 10 GPM I will still have about 31 PSI remaining of dynamic pressure? (or does it not work that way?)

    Bookmark   June 4, 2009 at 2:33AM
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Thanks everybody for the advice,

I was successful in replacing the 30Â service line with 1" copper.

Right before the service line enters the house (above ground here in no-freeze California) I put a 1" T and put a temporary branch to connect to the old galvanized pipe network, for now until I get around to replacing the rest of my pipes. I used ¾" PEX for about 4 to connect the new service line to the old galv network. I did use a little bit of copper pipe at the copper T to take the copper-PEX connection below ground so that the PEX would not be exposed to sunlight. The entire PEX run is about 8" below ground running along my foundation wall.

I also installed a 1" main shutoff ball valve where the 1" service line exits the ground to go into the crawlspace.

I found the 1" copper a little harder to sweat compared to the ¾".

BTW, at the new line copper T, right before entering the crawlspace, I remeasured the full throttle water flow and I was still getting 20 GPM after 30Â of 1" copper (63 PSI static pressure). So all looks good and on track for replumbing inside the house and finally being able to bring sufficient water supply to the back yard sprinklers.

Thanks much for all your suggestions.

    Bookmark   June 10, 2009 at 8:56PM
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