Increasing main water line size

[Pegasus501]

Hi guys, new homeowner here with a few newbie plumbing questions. I have been researching this for a couple days and these are the last few questions I still have..

My current system is a 3/4" copper pipe from the meter to the crawlspace with a shut off valve that seems to be reducing to 1/2" into a 1/2" PEX trunk line for about 30' through the length of the house. All the branches are 1/2" PEX.

I am trying to set up over-ground sprinklers and I am not getting enough flow with 1/2" tubing.

Questions are:

1. Since the the supply is being reduced into my home, how helpful would it be to replace the main trunk line from 1/2" PEX to 1" PEX considering it's only 30'? I would also replace the outdoor spigot branch to 1" PEX from 1/2".
2. Would I also need to replace the 1/2" main shutoff valve? Or would such a small piece not make a difference?

Thanks!

 

[WorthFlorida]

Increasing 30' up one size will will be OK but 30' increased to 1" may not make much of a difference from 3/4" but it wouldn't hurt. The section in the crawl space should have all be 3/4" before branching off to fixtures.

Is there a spigot before the 3/4" line changes to 1/2"? If there is it will allow to get a read on your flow rate and pressure. How many zones, sprinkler heads, approx area to irrigate? A 3/4" main may be enough if you tee off at the 3/4". Feed an irrigation system, 1/2" usually will not be sufficient unless it is a small yard. Changing the main to 1" may get complicated and expensive.

Generally, homes are feed with copper pipe, 3/4" is the feed looped around the home and then tee off with a 1/2" to the fixtures.

How old is the home? With all PEX was this a remodel?

 

[Sponsor]

 

[wwhitney]

1). Flow is determined by adding up the pressure losses for all the components between the water main and the outlet. Each component has a pressure drop vs flow curve, including the outlet, and as you turn the water on, the flow rises until the total pressure loss matches the available pressure at the main (adjusted for any elevation difference).

If the pressure drop is somewhat equally divided across multiple components, upsizing just one won't help much. But sometimes the pressure loss is dominated by one component, in which case upsizing it has a big impact. That sounds like it may be the case for you. If you try to draw 10 gpm through 30' of 1/2" pex, the pressure drop for that segment is around 27 psi. Upsize it to 1" pex, and the pressure loss is only about 2 psi, or a 25 psi difference.

So give it a try. If you have some other restriction before or after it, like a hose bibb with a tiny orifice, or a kink in your water lateral, you won't see much benefit, and you can try to track it down. Otherwise it should help.

2) Start with the easiest part, which means leaving the valve and upsizing immediately after. Then if that is insufficient, you can investigate whether upsizing the valve may help.

Cheers, Wayne

 

[Pegasus501]

Increasing 30' up one size will will be OK but 30' increased to 1" may not make much of a difference from 3/4" but it wouldn't hurt. The section in the crawl space should have all be 3/4" before branching off to fixtures.

Is there a spigot before the 3/4" line changes to 1/2"? If there is it will allow to get a read on your flow rate and pressure. How many zones, sprinkler heads, approx area to irrigate? A 3/4" main may be enough if you tee off at the 3/4". Feed an irrigation system, 1/2" usually will not be sufficient unless it is a small yard. Changing the main to 1" may get complicated and expensive.

Generally, homes are feed with copper pipe, 3/4" is the feed looped around the home and then tee off with a 1/2" to the fixtures.

How old is the home? With all PEX was this a remodel?

No spigot, just the valve from the copper 3/4" to the PEX 1/2". I'm thinking 1" main PEX to match the 3/4" copper. The sprinkler system will be 6 heads spread across 2 zones for a ~700sqft yard.

Do you think a much easier/cheaper option would be to just replace the 1/2" PEX line from the main shutoff valve with a 1" PEX, tee off into the water heater, tee off into the sprinkler area, then meet back into the already installed 1/2" PEX?

It is a 60s home and yes they had a remodel a couple years back because of a plumbing issue so I'm guessing they replaced everything inside with PEX. Why would they not match the 3/4" copper feed from the meter???

 

[Pegasus501]

1). Flow is determined by adding up the pressure losses for all the components between the water main and the outlet. Each component has a pressure drop vs flow curve, including the outlet, and as you turn the water on, the flow rises until the total pressure loss matches the available pressure at the main (adjusted for any elevation difference).

If the pressure drop is somewhat equally divided across multiple components, upsizing just one won't help much. But sometimes the pressure loss is dominated by one component, in which case upsizing it has a big impact. That sounds like it may be the case for you. If you try to draw 10 gpm through 30' of 1/2" pex, the pressure drop for that segment is around 27 psi. Upsize it to 1" pex, and the pressure loss is only about 2 psi, or a 25 psi difference.

So give it a try. If you have some other restriction before or after it, like a hose bibb with a tiny orifice, or a kink in your water lateral, you won't see much benefit, and you can try to track it down. Otherwise it should help.

2) Start with the easiest part, which means leaving the valve and upsizing immediately after. Then if that is insufficient, you can investigate whether upsizing the valve may help.

Cheers, Wayne

Thanks, I will be looking more into pressure drop vs flow and learn! That's good to hear, I wanted to make sure it would have some effect before I started buying stuff, crawling, cutting, and installing.

That's a very good point. Let's say I do see some improvements with the easier part. In your opinion, would going through the trouble of cutting off the utilities water, cutting off the valve, and increasing the size be worth it? I guess I'm asking is; does a reducing valve have a big effect on the system?

 

[Reach4]

Let's say I do see some improvements with the easier part. In your opinion, would going through the trouble of cutting off the utilities water, cutting off the valve, and increasing the size be worth it? I guess I'm asking is; does a reducing valve have a big effect on the system?

Worth it, yes. Turning off the water is not that big of a deal. Also, note that not all valves are full-ported. So your 1/2 inch valve may only have a 3/8 inch passage.

Let's see a photo of the current valve and the copper pipe.

 

[WorthFlorida]

At the valve from 3/4" to 1/2" it is best to have a ball valve full port. 3/4" in to 3/4" out. If you do not have copper pipe soldering skills or tools, Sharkbite and a few others have push and fit valves and adapters for all kinds of pipe.

Why 1/2" PEX was used is a unknown. Whom ever did it didn't know better, on a tight budget, didn't have 3/4" on hand or not enough fittings, on and on. One area is couplings used, the inside diameter of tees and elbows are smaller than the PEX itself compared to copper fittings.

Changing the main from the meter is not difficult, what originally stated meant it can be labor intensive. In Florida the water meters are at the curb just below the surface. My homes up north were all in the basements. If the meter is a certain distance from the home, trenching, getting below the frost line, any utilities in the way, trees roots, rocks and distance can make or break the effort. It's up to you if you can handle it.

For the irrigation, 700 sq ft is not much to worry about as compared to a 2000 sq ft yard. Thirty years in Florida and have used just about every type of sprinkler, I've settled down on Hunter MP rotors in pop ups . My present home I'm irrigating about the same amount of yours with three zones, one in the backyard, side yard and front yard. My front yard has 14 MP rotors (orange color) and most are 180 degree spray pattern, however, we have reclaimed water and the pressure is very high that was causing a lot of fogging and run offs with regular pop ups. My rotors are used in pop ups and it's a slow watering process to reduce run off and wasted water. Where I used to water for 15 minutes I'm now watering for one hour. Hunter's web site has charts on its sprinklers and MP rotor use about .5 gallons per minute at 40 PSI average but some are over 1 gallon. When you map out your irrigation you can make it three zones or even four. The days of using sprinklers that can dump a few gallons per minute per head for residential use is waning. Irrigation valves are 3/4" minimum and 1" valves are very common and used most often for residential use. You feed the zones with 1"valve, 1" PVC and tee off with 1/2" to the sprinkler for best performance. It's ok to feed the irrigation system with 1" pipe from a 3/4" source.

One last hint, when you tee off from your water source, you want the irrigation to be feed from the tee (center) tap so the domestic water runs straight through the tee. After the tee you can increase it to 1". There was a post sometime ago where every time the irrigation was on, it was sucking water from the home. The homeowner could hear air getting sucked into the shower head. It's why with a city water supplied irrigation, you do not want all the capacity your home is supplied with for irrigation.