1" meter, combine two 1" distribution lines

[jmurph]

Just built a large new construction house with two 1" meters, one for the house and one for sprinkler, both with 1" pex distribution lines running 300' to the house. Haven't been thrilled with flow rates/pressure drop during use. Pressure is 56 psi at baseline. When running two showers, pressure drops to 42 psi.

Hose bibs are hooked up to the irrigation meter and get same psi of 56. I get 8.3 gpm out of one hose bib, and pressure drops to 20 psi when running. When running 2 hose bibs, pressure drops to 7 psi and they have a combined gpm of about 12. I'm not sure if this is sufficient to run a sprinkler system or not.

First, would adding a booster pump help with this issue, or would I need to upsize the distribution lines? The irrigation system and sod have not been installed yet. Rather than upsizing both lines, would simply connecting both 1" lines to the house meter be feasible, and then upsize the irrigation distribution line separately? This would save a lot on pipe/trenching cost rather than upsizing both.

 

[Reach4]

Using http://www.pressure-drop.com/Online-Calculator/ and 0.875 ID for the pex, and 330 ft of water (extra to compensate for fittings etc), and 8 gpm I show about a 15 psi pressure drop expected. I always use 0,03 mm for roughness without thinking about it. You can do better if you like.

One test to consider is to run the water to irrigation, and no water used for the house, see how the house water pressure changes. That drop would be due to stuff before the paths split.

There is some drop from the meters.

Had you used 1 inch SIDR, the pipe would have been bigger -- over 1 inch OD.

Paralleling the two PEX pipes would reduce pressure drop in the pex by more than half. To predict that drop for an 8 gpm flow, find the drop for a 4 gpm flow. I got 4.22 psi drop when I tried that.

 

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[Jeff H Young]

assuming the irrigation is dirty water? why 2 meters otherwise.
personally would have ran bigger line than 1 inch on 300 foot run but don't know how it comes out "by the Book"

 

[Reach4]

assuming the irrigation is dirty water? why 2 meters otherwise.

I presumed it would be because there is no sewer charge for the irrigation usage.

 

[jmurph]

Using http://www.pressure-drop.com/Online-Calculator/ and 0.875 ID for the pex, and 330 ft of water (extra to compensate for fittings etc), and 8 gpm I show about a 15 psi pressure drop expected. I always use 0,03 mm for roughness without thinking about it. You can do better if you like.

One test to consider is to run the water to irrigation, and no water used for the house, see how the house water pressure changes. That drop would be due to stuff before the paths split.

There is some drop from the meters.

Had you used 1 inch SIDR, the pipe would have been bigger -- over 1 inch OD.

Paralleling the two PEX pipes would reduce pressure drop in the pex by more than half. To predict that drop for an 8 gpm flow, find the drop for a 4 gpm flow. I got 4.22 psi drop when I tried that.

- Thank you so much for the great advice! I was advised to use a 1" line, but in hindsight, I should have found this great forum prior to trenching it to prevent this issue.

- I did test high flow on each meter, and the pressure on the other stayed up independently letting me know the restriction isn't upstream of the meter.

- You are correct I don't have to pay sewer on the irrigation meter, thus beneficial having two.

- I think it might be best to join the two 1" together for the house, and then run a separate 1.5" for the irrigation (or vice versa). Looks like a 1.5" will outperform the two 1" lines, but not by a lot. May use the 1.5" for the irrigation system since it would have higher flow rates. I'm calculating a 5.1 psi drop at 12 gpm for a 1.5" vs a 8.8 psi drop at 6 gpm for a 1" line.

 

[Reach4]

May use the 1.5" for the irrigation system since it would have higher flow rates. I'm calculating a 5.1 psi drop at 12 gpm for a 1.5" vs a 8.8 psi drop at 6 gpm for a 1" line.

See the IDs on https://www.jmeagle.com/sites/default/files/JM Eagle_HDPE_WaterService_IPS_CTS_SIDR.pdf

I would tend not to use 1.5 inch PEX. But if you do, https://www.engineeringtoolbox.com/ASTM-F876-PEX-tube-d_2139.html has the sizes.

SIDR polyethylene, the kind used with barbs, is bigger than the same nominal size with most other pipes.

Many people use IPS or CTS size poly pipe for water service, and there are compression fittings made for the purpose. I don't know much about the compression fittings. CTS and IPS sizes have constant OD for a given nominal size. SIDR has a constant ID for a given nominal size.