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what diamter pipe from outside faucet to garden faucet ?

what diamter pipe from outside faucet to garden faucet ?

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  #1  
Old 03-27-17, 04:26 PM
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what diameter pipe from outside faucet to garden faucet ?

I want to extend an outside faucet, which is on the wall) and connect a section of 100ft polypipe to a vegetable garden (and other areas to be watered).
The polypipe will be going underground but I'm wondering what diameter to use.
The outside faucet is 1/2" standard. I presume I will lose pressure if I put a 1" polypipe connected to that?

Secondly, I have a spare pressure tank. If I was to connect the pressure tank at the garden end, is there a switch that can open and close a valve? The only pressure switches I have seen run electric pumps. I would want this to open the valve when below 30psi, and close when above 50psi.
 

Last edited by qwertyjjj; 03-27-17 at 05:07 PM.
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  #2  
Old 03-27-17, 06:00 PM
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1" polypipe would be fine. The pressure you have at the end of the poly pipe will be the pressure at the faucet, minus the pressure drop of the poly pipe at the desired flow rate. Pressure drop of larger pipe is lower than that of smaller pipe at same flow, so using larger pipe is to your advantage.

A standard pressure switch used for well pumps can be used to control a solenoid valve instead of a well pump. The switch doesn't care what is connected to it. You would wire 120 volts to one side of the switch contacts and a 120 volt solenoid valve to the other side of the contacts. You could also use a low voltage solenoid valve; just make sure the power source connected to the switch matches the valve requirements.

You would want a normally closed valve (closed when no power applied).

[edit]: Note you must have a vacuum breaker on the faucet, and if you make the connection to the polypipe permanent, you must have a dual check check valve between the supply and the buried pipe to prevent any chance of contaminating your water supply with dirty water.
 
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Old 03-27-17, 06:16 PM
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  #4  
Old 03-28-17, 05:37 AM
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I see no benefit to installing a pressure tank and switch out in your yard. You will always be limited by the 1/2" and spigot at the house. The pressure tank could provide a better flow as long as the pressure tank was full but that's a very small volume of water when watering a garden and would hardly be worth the expense. The only thing you can do that would provide a serious benefit is to add a booster pump but I would connect your garden watering line to something other than a spigot on the side of the house. Running a 1" or 3/4" line directly from the supply line in your house would be my first step.
 
  #5  
Old 03-28-17, 10:11 AM
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[edit]: Note you must have a vacuum breaker on the faucet, and if you make the connection to the polypipe permanent, you must have a dual check check valve between the supply and the buried pipe to prevent any chance of contaminating your water supply with dirty water.

Doesn't the anti siphon provide enough to prevent contamination?
Also, what's the benefit of a dual check valve rather than just a normal one way check?

I would have to drill through concrete to get the supply line to go outside, which is much harder as it's also 6ft below.
 
  #6  
Old 03-28-17, 10:21 AM
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If you have a 1/2" spigot connecting to a 1" poly going into the pressure tank but 1/2" out of the tank then isn't the pressure tank always going to fill faster than what is watering the garden?
Other option is just watering valves and an irrigation controller.
 
  #7  
Old 03-28-17, 10:48 AM
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It's always best to check your local plumbing code to determine what is accepted in your area. Generally connections between potable water and underground irrigation plumbing are considered high hazard connections. The code will spell out what type of backflow prevention is approved for high hazard connections. Generally a redundant protection is required, meaning failure of one part of the valve won't allow cross contamination. A dual-check check valve is one such valve; there are others that may be approved in your area.
 
  #8  
Old 03-28-17, 11:56 AM
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Your system is always going to be limited by how fast the water comes out of your spigot at the house. A pressure tank can only store water. And, a pressure tank stores a small fraction of it's size so it's not a good option for storage. The pressure tank gallon size you see on the box describes the size of the metal housing. It's actual capacity to hold water is much, much less. For example a 42 gallon pressure tank operating on a system set to 40/60 psi only holds about 5 gallons of water. Out at your garden you can have increased flow volume (but not pressure) for the first 5 gallons then after that you're back to what your spigot at the house can put out.
 
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