Hi Greenthumbnick,

What a nice layout. Just a few questions to aid myself and other to provide meaningful suggestions.

1. Pressure at the house spigot? You can measure this with a pressure gauge sold at HD or Loewes for around $15.
2. Flow rate from the spigot (gallons per minute)? Time to fill a 5 gal bucket would suffice.
3. Area of each planting section? Can be converted to gallon used per week.
4. Any large trees nearby? Full sun or partly shade?
5. Are the beds built?
6. Will you want to automate the system?

You have a good plan but need to calc the details. 1.5 to 2" line recommended for the long length of PVC main. This would save your pressure loss along the main to the garden. In the garden 3/4 to 1" would be okay from the main to the drip. This is general info and maybe bigger than you need, but I wouldn't know until the answers are given.

The picture really helps.

Aloha for now.

lehua,

Thanks for the response and compliments.

1. Not sure, was planning on buying a gauge tommorow.
2. Will get that tommorow, I imagine its up there since I have a 1" main to the house.
3. Tough to say. I have sandy soil and in the dead of summer it drinks lots of water.
4. No trees, Full sun
5. Beds are built, this will be the second year for the garden.
6. No need for automation. I thought about connecting it to my existing sprinkler system as an additional zone but that would be way too much work since there werent any extra wires preinstalled for more zones. So just turning on the spigot on the side of the house will work just fine for us.

Hi GTN,

The flow test is important (5 gal bucket timing). Your pressure is related to the reservoir water level height for your subdivision or community. Usually it is about 65 to 85 psi or located about 150 feet above you house slab. Some communities have low pressure zones but you would know that if your street was in one (fire protection). If the pressure is high from the street you will have a pressure regulator in your garage that keeps the pressure at about 55 psi in order to protect your water using appliances and your faucet seals. Your one inch main line has no effect on the pressure but it helps the flow capacity to your house when you want or need it. Your pressure gauge will tell you if your pressure regulator is working or needs adjustment.

Remember to install a vacuum breaker valve at the house spigot before your hose unless you remove the hose every time you water. If you going to do that quick couplings would be useful to install. I know this is more than you really wanted to know. Sorry, Aloha.

lehua,

I just checked the pressure, its 78-79 PSI. I didnt get a chance to check the flow rate, hopefully I'll be able to get to that in the morning.

Thanks for the info on the vacuum breaker valve and quick couplings. Not sure what they are but I'll look that up. LOL

Did a flow rate check this morning. 5-gallon bucket filled to the rim in 38.1 seconds.

Hi GTN,

Here we go. Your flow rate is approx. 8 gallons per minute or 470 gallons per hour. Others can chime if I go astray. A particular pvc size allows a certain flow at a certain velocity. You should not exceed 5 feet per second (velocity). The bigger the diameter of pipe the lower the velocity and friction loss for your mainline. You could use a one inch line for your main because you have such high pressure and a small loss versus more economical pipe would be okay in your case. I would recommend 1 1/4 to 1 1/2". This would bring the velocity to 1.8 fps which is good non-turbulent flow. Your system should be design to 80% of your flow rate which is 6.8 gpm or 400 gph. Your drip emitters or tape is rated for certain gpm or gph. Add all the output of emitters in gph and do not exceed the 400 gph and that is the a zone capacity. If you need more water output then start another zone. That is the system design side.

Now measure your plot areas and you will be able to calculate your water demand. You should balance your system output to the garden's evapotranspiration or demand. This means when you hand-water how long you need to let the system run and not waste water outside of the root zone.

If you have someone else do the work and design, this info can help you check their sales pitch.

By the way is the spigot coming out of your house system or off your yard irrigation. Your pressure is high for a house but about average for the street pressure before going into your house. You should have a pressure regulator in your house(garage usually). This high a pressure needs a pressure regulator in you system to lower the pressure to recommended manufacturers levels for the emitters or drip take you use. If you don't your fittings or the tape will start to self destruct. GL Aloha.

Lehua,

Thank you for the detailed explanation. I will need to re-read it and digest it a little.

The pressure is from a spigot coming from the house. I will look into it and probably have to call my builder back.

Thanks again for your help.

Nick

Hello again GTN,

Call your water company as well, they are a wealth of good information along the topic we are discussing. They are a good check for information you get from the builder. They are the experts for your area and always willing to help. Also check your appliance manuals concerning their operating or working pressure. It will help enable them to last longer in good service. Aloha.

For what its worth, the last time I checked into the prices for 1 1/4" and 1 1/2" PVC, the 1 1/2" was cheaper. the guy said it was because there is little demand for 1 1/4". Whatever.

Also, I use polyethlene tubing for my laterals that will be hooking directly to drip tapes, but then I don't bury those laterals usually.

And now my last 2-cents. I have never found myself putting in too many valves in a drip system but have occasionally wished there were more. The reason for more is the ability to isolate various beds during the growing season. For instance: if you had a 3-zone system and no more valves, it would not be possible to shut off a part of the garden when it no longer needed irrigation later (or very early) in the season when the rest of the garden did. If your water is cheap or you don't mind wasting it, it isn't an issue. Best of luck, when it is in the way you want it you'll love it.

Michael

Thanks for all the great information.

I was just wondering...Since Im connecting this irrigation system to an outdoor spigot does it make sence to make the pvc wider than the spigot? I assume spigot is 3/4". Does it do any good to make the pvc 1" or 1 1/2"?

Thanks.

Hi GTN,

Very good question. I'll bet your 3/4" spigot has a 1/2" copper line feeding it nor is a spigot 3/4" through out it's length. Smaller to bigger or vice versa doesn't matter. Size affects velocity at that change point, but very briefly. Length of pipe is what affects the system efficiency (loss of pressure) the most. Water flows faster through the smaller diameter pipe and when water velocity gets high enough turbulence in the pipe is reached and your friction loss per foot of pipe increases as well as noise. This friction loss robs you of pressure as the water travel along the system. Your system has high pressure so this not a big concern in your system. It becomes a design issue depending on where you reduce your pressure for your garden.
1 1/4" pipe was sized by a formula that calculates flow versus velocities in various size pipe. A standard design criteria for non-turbulent flow is less than 5 feet per second velocity(noise reduction). Using that criteria the 1 1/4" was acceptable, 3/4" would be less acceptable but still can be utilized with no real problems. It then becomes a cost issue. It makes no difference what size the source pipe is, but hooking up to your house affects the velocity of water traveling through your house pipes. If you turn on your hose, how noisy is the flow in your house? Does it affect the flow of other water using appliances being used at the same time? Turn on the washer, shower, kitchen faucet, etc an listen to the sounds of the water. If the answer is no to these questions your house water system doesn't pose a constriction to your garden water needs. The more items being run the noisier it gets. Did you ever call your builder and find out about the pressure regulator needed for your house water system? Just curious. GL. Aloha