Automatic watering for raised beds.

gmanar(7 CLT-NC/ HZ 7)April 1, 2014

Hi All,

I started gardening last year, things went fairly well... but I was unable to keep up the watering schedule (manually) - in summer. So this year i wanted to do something for automatic watering.

I decided i would go with PVC pipes as in the link shown - It works well. I have 2 15X3 beds. so I have 2 pipes on each bed (one to the left one to right) - each 15 feet long.

Now for the problem: I can run the water to one bed at a time - and the pressure is enough to drive it, but if i try to water both beds at the same time then there is no pressure. I am getting 60 PSI from the outlet (at the outlet) - it is about 80 ft away from the beds - and the beds are on a kind of hill about 2 ft higher than the water outlet level.

Why both beds at the same time ? - nearest water outlet to the beds is about 80ft away - and i dont want to run 2 lines out there.

Is there any way to increase the pressure ? or any other ideas ?

As always any help is greatly appreciated.

Thanks and regards

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zeuspaul(9b SoCal)

First you need to minimize the losses. What is your flow rate? Measure how long it takes to fill a five gallon bucket at the spigot. Then measure how long it takes to fill the same bucket at the end of the 80 ft run. To minimize loss here you will probaly want to use a 3/4 inch hose The two feet higher is negligible. Are you using a garden hose for the 80 ft run or PVC?

Then you need to reduce the number and/or size of the drilled holes. Using the video as a guide you could easily use half the number of holes.


    Bookmark   April 1, 2014 at 11:54AM
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gmanar(7 CLT-NC/ HZ 7)

currently i am running a 100ft garden hose.

The eventual plan is to get the poly PVC (black pipe) - so i might do it now and see if the 3/4 inch makes the difference.

I will also try to get a 5 gallon bucket and report back the time.

Thanks for the suggestions.


    Bookmark   April 1, 2014 at 1:14PM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

Couple of points. First, if you want to spend the money you can buy inline pressure boosters but they aren't cheap.

Second, I am concerned that you are approaching this with "what's good for one is good for all" mindset. In other words assuming that all the plants in your garden require the same amount of water and at the same time. That approach can create all sort of problems for you because it simply isn't true.

A watering schedule usually does more harm than good because it is so inflexible and disregards the real and different needs of the plants. It is convenient for the gardener but not so for the plants. EX: providing an ideal watering schedule for leafy greens will easily drown pepper plants and dilute any tomato flavor. For deep rooted plants to get enough water any nearby shallow rooted plants will develop root rot and die.

An auto system sounds good in theory but is much more complex in reality. That's why most of us who use auto watering set-ups lay them out in multiple zones and we plant accordingly. You have 2 zones already and may find you want to capitalize on that fact (or better yet increase it to 4 zones) rather than eliminating what you see as a problem.

So what specific plants are you growing, how do their water needs differ, how do those water needs change during the season as it gets hotter and cooler and the crops change, and can your layout be altered to accommodate more flexibility?

Just some things to consider.


    Bookmark   April 1, 2014 at 4:09PM
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Pressure by itself doesn't tell the whole story. You need to know what happens to the pressure when the water flows. In your case, once the water begins to flow, the pressure is apparently dropping off due to pressure drop in the 100 foot hose. The easiest way to fix this problem is going to be to reduce the flow rate by using fewer or smaller holes as Zeuspaul said. Once you do that, the pressure drop in the 100 foot hose will be reduced, and there may be enough pressure available at the beds to deliver water evenly. Obviously, with a lower flow rate, the water will need to be turned on for a longer time.

Another idea is to put a hose Y out near the garden beds at the end of the 100 foot hose. Put a separate timer on each bed, and adjust the timers so that they are not on at the same time.

There are also multi-zone timers. You could put one near the beds.

There is a possibility that the 100 foot hose run is not the cause of your pressure drop. The pressure drop could be caused by the pipes leading from the water source to your spigot.

Also inspect any valves or whatever else you may have inline. Sometimes the valves have very small openings and cause a significant drop at higher flow rates. If it is possible to eliminate the valves, this could be another easy solution.

Good luck.


    Bookmark   April 1, 2014 at 4:26PM
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zeuspaul(9b SoCal)

gmnar. You don't need a five gallon bucket. You can use any size of known quantity. You could use one gallon but the results won't be as accurate.

What size is the hose? 1/2, 5/8 or 3/4?

You can vary the water flow per plant by using more or less holes per plant. Also the last holes may distribute less water. You can use a larger hole or two holes towards the end to compensate for less pressure at the end of the run.

But first things first. We need a flow rate at the beginning of the run at the spigot and one at the end of the 100 ft hose. The spigot flow rate is what you are stuck with. The flow rate at the end of the hose tells us how much flow you are losing due to garden hose friction.

Without the the two flow rates and also the number and size of the holes it is difficult to make any recommendations.

What size holes did you drill and how many per bed?


    Bookmark   April 1, 2014 at 10:08PM
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gmanar(7 CLT-NC/ HZ 7)

Thanks everyone for all the responses.

Some more details - I have 2 beds 15X3 - about 90 feet from the house. I have 4 white pvc pipes in the beds, the pipe is about 8 inches above the bed. There are 3 holes - every 6 inches. The holes are drilled using #57 Micro Drill Set - it is smaller than 1/16. Each of the pvc pipe has a valve to control the amount of watering - that way i can control the amount of water depending on what i have planted in there.

Currently i am running a 100 ft 5/8 inch garden hose (regular hose) - from the water outlet to the beds. There are no holes or leaks in the hose - just in pvc.

I think over this weekend - i am going to measure the waterflow - at every stage:
1. water outlet
2. end of the hose
3. end of hose + a valve
just to get an idea where it is going south.
I like the idea of putting a timer, but then i am going to have timer at the main outlet - so if the main outlet is configured to turn on every other day for 30 mins - then i have to configure the second set of timers at the bed to turn on - one precisely at the same time - and the other at +15 mins...
That sounds fairly complicated :) - so i might just run another pipe till there and use the main timer to control and not have 2 more timers at the bed.

but i am surprised that there is not enough pressure :) so trying to find an easier way :)

really appreciate all the help. I will post my findings around the weekend.

    Bookmark   April 2, 2014 at 9:31AM
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gmanar(7 CLT-NC/ HZ 7)

I was able to measure the water flow :
At the spigot - it took 33 seconds to fill the bucket i had ( i am not sure if it is 5 gallons - but looked close to it).
At the end of the hose - it took 37 seconds to fill the same bucket.

Also i was able to connect the 3/4 inch poly pvc line to test. There was no significant change - i still was unable to run 2 beds (4 pipes) at the same time - i was able to run 1 bed (2 pipes) very well - and 3 (pipes) fairly well.

I think my option now is to run a single line till closer to the bed - then almost at the bed - put a 2 zone timer.
Any other ideas ?

Thanks and regards

    Bookmark   April 3, 2014 at 11:51AM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

if the main outlet is configured to turn on every other day for 30 mins

This is drip irrigation? Only run for 30 mins? Every other day?

That would result in very frequent shallow watering (and produces water-dependent shallow rooted plants) rather than the less-frequent deep watering needed for most plants.

Depending on soil type and plant needs, 2-3 hours every 7-10 days is a commonly recommended schedule. 30 mins just doesn't allow for much water in only 30 mins. Plus it sounds like your system hangs above the beds rather than having soil contact, correct?


    Bookmark   April 3, 2014 at 12:20PM
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zeuspaul(9b SoCal)

Did you measure the time with the 3/4 pipe? It has to be more than the garden hose. You are getting about 9 gpm at the spigot and 8 gpm at the end of the hose. You would get about 9 gpm at the end of the feeder line if you used one inch pipe. But it isn't enough to run the four pipes. Every little bit helps.

Even if you can get the last ten percent increase it won't be enough to solve your problem. I would use two holes every six inches instead of three. That would be about a 30% decfease in flow rate which should enable you to run 4 pipes.

Try experimenting by blocking some holes with tooth picks or pins. Start by reducing from three to two closer to the feed line. Pressure should be higher at the beginning of the runs. Two holes early and three towards the end might give even flow rates.

Are you using sufficient sized pvc tees and? after the main feeder?


    Bookmark   April 3, 2014 at 2:13PM
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wayne_5 zone 6a Central Indiana

I would think that 2 beds of 15x3 would be a snap to hand water compared to the fuss and danger of a setup that is hard to control.

    Bookmark   April 3, 2014 at 7:16PM
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jean001a(Portland OR 7b)

Drilling holes in a pipe does not mean it is a *drip* system.
Thus, 30-minute run time may be more than enough water rather than too little.

Why is it that you want to avoid soaker hoses or inline drippers?

    Bookmark   April 4, 2014 at 12:39AM
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I think you should be able to solve the problem by just reducing the flow rate to something more manageable, for example by blocking off holes as Zeuspaul suggests.

However, I would like to point out that there is no need for a timer at the spigot if you use a two-zone timer. Leave the spigot on all the time and just run the hose to a two zone timer near the two beds. (Or you can run the hose to a Y near the beds and put a separate timer on each branch of the Y). There is some danger of wasting a lot of water if the hose springs a leak, but hopefully you will notice and correct the problem.

I don't think I would pay extra money for 3/4" hose just to get from 37 to 33 seconds. If it saved you from buying an extra timer it could be worth it, but it seems like it won't make enough difference in your case.


    Bookmark   April 4, 2014 at 1:36AM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

Drilling holes in a pipe does not mean it is a *drip* system.
Thus, 30-minute run time may be more than enough water rather than too little.

Good point Jean but the cuts in most drip tapes are much larger than the ones the OP described so from his description I figured the odds were more likely drip than spray.

At least with drip tape you can calculate gph. With this set-up, who knows.


    Bookmark   April 4, 2014 at 9:57AM
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gmanar(7 CLT-NC/ HZ 7)

Hi All,

Thanks so much for the valuable input.
Finally i decided to scrap the idea. I am going to pull out the pipes this weekend. ( i will use the pipes to for the mini green house i am planning to build this winter :) )
I think for 2 beds of 4X15 - it is easier to hand water them, also i have some cinder blocks along one edge with garlic - and blueberry bushes there ... so even if i automate just the beds i still have to hand water the rest. I thought long and hard about automating those as well - but i think the complications and the maintenance of the automated system just is not fit for the size of the garden i have.

I learnt a lot - and again thanks for all the help.


    Bookmark   April 8, 2014 at 9:12AM
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