maintain pressure in garden hose

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  #1  
Old 05-25-15, 07:26 AM
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maintain pressure in garden hose

I have a very basic irrigation system setup.
200ft of garden hose from an outside tap goes to 3 separate areas:
1st a splitter, where a drip hose system is attached, not open on full so pressure is very low.
2nd area connects to a soaker hose covering 100sq ft garden,
3rd area just nearby is another soaker hose connected to the 1st soaker hose for a 75 sq ft garden.

Obviously the last soaker hose doesn't have much pressure and the garden hose has variable pressure depending on sunshine or not.

How can I maintain the pressure in these hoses over that distance and possible extend it in future?
 
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  #2  
Old 05-25-15, 07:54 AM
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Are all of the hose(s) of the same diameter ?

Must they all be used simultaneously ?
 
  #3  
Old 05-25-15, 08:48 AM
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They do not have to be used at the same time so I could put a parallel connection on them instead but that would involve an extra timer at the junction point?
 
  #4  
Old 05-25-15, 09:40 AM
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You either need a larger hose or a booster pump. I'd replace the 200' of garden hose (probably 5/8") with 1", 1 1/4 or 1 1/2" black poly pipe. The bigger the better. That would give you good flow volume and minimal resistance over the long run. You'd still be limited by the spigot feeding the pipe but at least you can get rid of most of it's flow resistance.
 
  #5  
Old 05-25-15, 11:44 AM
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How does the flow (extra water in the pipe) help?
Wouldn't that make it lower pressure as you have a 5/8 tap pushing a 1" pipe?
 
  #6  
Old 05-25-15, 12:33 PM
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You first need to understand that "pressure" is merely the resistance to flow.

Let's assume that you have a 10,000 gallon tank of water and the level of the water in that tank is 100 feet above the tank outlet. Let's further assume that you have an unlimited supply of water to that tank and there is an overflow at the 100 foot level. That means the water level in the tank will always be exactly 100 feet and you will always have a constant pressure of 44.3 psi at the tank outlet.

Now add a 6 inch inside diameter hose to the tank outlet. Run the hose out 100 feet (or any distance you desire) but keep the end of the hose at the same level of the tank outlet. Put a valve on the hose end and a pressure gauge just upstream of the valve. With the hose-end valve shut the pressure gauge will read 44.3 psi. Slowly open the valve and the pressure gauge will remain at 44.3 psi until you get the valve fairly well open at which point it will start to fall in pressure. At this point the valve opening is allowing the maximum flow through the hose. Further opening the valve will allow more water to leave the hose/valve than can enter from the tank and the pressure at the hose end will drop. However, the pressure at the hose inlet is still 44.3 psi. The pressure drop at the end of the hose is a result of friction between the flowing water and the hose itself.

Now let us disconnect that six inch hose and replace it with a one inch hose. Make the one inch hose five feet long and then couple it to the inlet of the six inch hose. Close the valve on the end of the six inch hose and measure the pressure, it will be 44.3 psi. Open the valve on the end of the six inch hose slowly and you will find the pressure will start to drop with a much smaller opening of the six inch valve than it did when before adding the short one inch hose. In fact, by the time the six inch valve is half open, maybe less, the pressure at the gauge will be at zero or just slightly higher yet the pressure at the tank outlet is still 44.3 psi. This loss of pressure is due to the friction of the water through the smaller one inch hose as its flow capacity is maybe one-sixteenth that of the six inch hose.

ANY restriction of flow will result in a lower pressure downstream of that restriction. Go to the home center and look at hose valves. You will find some that have a through-hole as small as 3/8 inch. How could you possibly get enough water through a 3/8 inch hole to completely fill a hose with a 3/4 inch inside diameter and no restriction on the outlet? You can't! In other words, you cannot flow any more water through your pipes and/or hoses than is allowed by the smallest section of you r piping system.

Many years ago it was NORMAL to supply water to a single family house through a 1/2 inch galvanized steel pipe from the water meter. The water meter was supplied from a six, eight or larger inch water main in the street BUT with a 5/8 inch copper (or often lead) pipe. The supply from the street main was virtually unlimited but the severe resistance to flow offered by the 1/2 inch steel pipe was such that the maximum flow at the house was maybe seven gallons per minute, maybe as high as ten gpm depending on the pressure in the city main.

So, your "problem" can only be solved by increasing the size of the supply piping, maybe all the way back to the municipal main, OR by reducing the flow requirements downstream at the point of use.
 
  #7  
Old 05-25-15, 12:46 PM
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I should add that's it's supplied by a pressure tank in the house fed by a well.
The pressure tank PSI varies from 30-50 PSI depending on where it is in the cycle and feeds an outside tap (half polypipe from the tank, some copper pipe in the wall).
So I can get 200ft of polypipe and connectors to connect it to a 5/8 spigot?
However, at the end of the polypipe it will have to go back to 5/8 connector to connect to the garden equipment and garden soaking pipe. Changing it back to 5/8 reduces the flow again?
 
  #8  
Old 05-25-15, 02:05 PM
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Your flow rate is limited by the flow from the pump system and the well (I assume a well) and the interior size and length of all the piping. The well has a finite amount of water available to the pump, the pump and tank has a finite flow rate as does all the piping. If the flow rate at the end of the piping exceeds any or all of the aforementioned there will be little or no pressure at the end of the piping. The ONLY way to increase the pressure at the end point is to decrease the total flow at the end point. It is like having a garden hose run out the end and having little pressure but if you hold your thumb over the end, reducing the flow, the pressure increases.
 
  #9  
Old 05-25-15, 03:00 PM
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Pressure, flow and resistance are different monsters. No matter how small or how long your hose the pressure will be the same everywhere as long as no water is flowing. Once you start moving water the walls of the hose and restrictions of fittings create resistance which drops the pressure. The further you go the more resistance and drop in pressure.

Your situation is not perfect. So, no matter what you do you will never get more flow and pressure than is provided right at your house at that initial spigot. That's it. That's all you'll get without adding a booster pump. So, you need to focus on not wasting away that very limited source.

Think of sticking your hand out a car window. When you are going slow there is not much resistance but your same hand at higher speed has much higher resistance. It's the same for the water in the pipe. To get 5 gallons a minute through a 5/8" garden hose it must move much faster than it would through a 1 1/2" pipe. The faster the water moves the more resistance it has against the walls of the pipe/hose. In a big pipe the same volume of water can move more slowly with less contact with the pipe walls and less resistance.

Just keep in mind that the hose bib at the house is as good as it gets. Everything you add after it only reduces performance. Nothing you do short of adding a pump will improve on what comes out of the spigot.
 
  #10  
Old 05-26-15, 05:28 PM
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What can I put in the middle then?
A compressor? If so, what type?
Or if I tap in a new poly line from somewhere else in the house, will the pressure be improved?
 
  #11  
Old 05-27-15, 12:21 PM
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You could install an auxiliary pump that has the required pressure and flow but it would still not output more than is available at the pump inlet. If this is an intermittent operation you could install a tank on the suction side of the pump, most likely with a float valve for automatic filling, and then the pump could supply the requisite amount of water at the proper pressure as long as there was water in the tank. Of course, if the need were to continue for a long period time you would need to have a large tank and there would be time periods when the tank is refilling that the full output of the pump would be unavailable. This makes the tank/pump idea unworkable in most situations.

Without wanting to re-pipe all the way back to the source I'm afraid that you are stuck.
 
  #12  
Old 05-27-15, 12:38 PM
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I'm having difficulty keeping in mind that this is just a couple hundred square feet of garden (total), not acres and acres of tillage.

Are they absentee gardens ?
 
  #13  
Old 05-27-15, 01:31 PM
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It's 2 gardens of about 10sqft
And an area for vines and bushes about 400sqft (to be watered in the future)
Pressure is still too low to do the 2nd garden so maybe I could split the pipe and do a timer on each at different times.
They are left absent for 5 days at a time.
 
  #14  
Old 05-27-15, 03:49 PM
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Running several zones, whether sprays, drips or soaker hose, controlled by a standard irrigation controller is an excellent method to use under these circumstances. Properly set up it will require very little "hands-on" time for proper operation.

Describing the results desired in detail is always beneficial in getting the right information.
 
  #15  
Old 03-25-16, 02:28 PM
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As polypipe is a bit more rigid, would this help instead of garden hose that expands in the sunshine?
I have some battery operated timers, which separated 3 zones last year so it kind of worked but it wasn't excellent.
Pressure in the soaker hose was low.
I had a sprayer which worked but that's not ideal for the fruit and veg as they get wet every day.

WHat I was thinking is to install polypipe from the pressurised water reservoir out 200ft to a tap by the garage and then that would supply the vegetable garden nearby.

It's worth noting that the garage is about 15ft higher than the garden so maybe I could install a water tank at the garage and have it feed the gardens by gravity?

Lastly, there is an old shallow water well about 150ft from the garden - maybe this could be used with a water pump? Only problem would be how to separate the 3 zones as the pump isn't triggered by a tap opening in one of the zones.
 

Last edited by qwertyjjj; 03-25-16 at 02:50 PM.
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