Dealing with low pressure when using a garden can be a headache. Garden hoses range in size from 3/8-inch, 5/8-inch, 1/2 inch to 3/4 inch in diameter. It is a good idea to choose the best size garden hose for low water pressure to ensure your water your plants without any challenges.
According to science, please allow me to be a bit technical, changing the size (diameter) of a hose does not change the static pressure of the water but rather the velocity and the dynamic pressure. This according to the legendary Bernoulli’s principle.
In the US, most outdoor/garden spigots are either 1/2 inch or 3/4 inch and in order to benefit from the effects of reduced diameter and increase in velocity, the best hose size for garden hose for low water pressure is 3/8 inch in diameter.
Using a garden hose whose diameter is smaller than the garden spigot/ Hose bibs / outdoor faucets, will result to an increase in the velocity of water in the pipe. This means the water jet can reach more plants while watering from one point.
Based on the above principle and my experience using water from a low-pressure source, the best garden hose for low water pressure was found to be Garden Flexeel.
Relationship between Water Pressure and Pipe Diameter
To deal with water in a garden hose, we will be varying the diameter of the pipe from ½ or ¾ inch (garden spigot size) to 3/8 inch (garden hose size). When the diameter of the pipes changes, the mass flow rate remains constant, this means that the water has to travel faster to compensate on that change.
This means that connecting a garden hose with a smaller diameter (smaller cross-sectional area, A2) result to an increase in water velocity but decrease in static pressure. However, an increase in dynamic pressure occurs.
This results to water shooting in the air and thus one can reach more plants when watering.
If your garden is not very large, it is advisable to go for a shorter hose (25 feet) to minimize on friction between water and pipe, though minimal it slightly affects the final mass flow rate.
What is Classified as Low Water Pressure for Outdoor Spigot?
The average water pressure for outdoor garden spigots is usually 45 to 55 PSI. For water to be termed to have normal pressure, it should range between 40-60 PSI. Anything below 40 PSI is termed as low water pressure.
When the pressure exceeds 70 PSI, it is considered to be high water pressure and is likely to damaged some garden appliances. However, in some households where the garden spigot is connected to directly to main water line (before going through the pressure regulator), the pressure can be as high as 110 PSI and the use of pressure reducers become very necessary.
For low water pressure, various methods can be used to solve the issue
Why 3/8-inch Garden Hose is the Best for Low Water Pressure
You might still be wondering, is the 3/8-inch garden hose really the best for low water pressure? Will it deliver a good volume of water? Yes, the 3/8-inch hose is the most ideal for low pressure.
The mass flow rate (volume) of water delivered by the smaller hose will be almost the same as the volume delivered by a larger diameter pipe. The small difference in volume usually occurs due to the friction between the water and the pipe. This is almost negligible.
I hope by now you are no longer asking the ‘does hose diameter affect water pressure?’. As you have seen from the principle above, a decrease in hose diameter results to increase in water velocity and dynamic pressure of the water.
Water Pressure and Length of Hose
Some people usually wonder, do you lose water pressure the longer the hose? Yes, there is a loss in pressure but not very significant. This usually results from the friction between the water and the walls of the pipe.
A good example of pressure loss based on measurements is that for a 3/8-inch garden hose having a flow rate of 3 gallons per minute, there is 50 PSI loss of pressure for every 100 feet.
This is why we recommend going for shorter hose (about 25 feet). Nevertheless, the flow rate also decreases.
Elevations also results to a loss in pressure if the pipe is not working on a level ground. For example, if one is watering plants at a heigh of 25 feet above the spigot, the loss in water pressure is approximately 11 PSI.
Other factors that affect water pressure include water temperature, smoothness of the hose interior, fittings, and style.
Methods of Increasing Water Pressure in a Garden Hose
Apart from choosing the best size garden hose for low water pressure, one can also consider increasing the water pressure in their garden faucet /spigot.
If your garden faucet is releasing water at a very high pressure when the garden hose is detached, the problem might be the length of the hose, constrictions, or leaks or any type of obstruction.
Low water pressure from the outdoor spigot can be caused by various issues which include leaking pipes, pressure regulator, clogged pipes, corrosion in the pipes or spigot valve, or low water pressure from the city or source.
The following methods can be used to solve low water pressure issues.
- Check for Leaks
The first step is to inspect the supply pipe for any leaks which can result to a low water pressure. Some damage can occur under the house or along the walls.
Check for wet surfaces to as fast indicators of leaks. The next step is to turn off the each and every faucet and all the water appliances in the house.
This is followed by inspecting the water meter to see if it is spinning. If no appliance is using water in the house and the meter is spinning, there is a leak in the house.
This can be confirmed by checking on the plumbing technical drawings and following pipes in the house to see any presence of wetness or leaks.
You can also hire a professional plumber to do the checkup and test the pipes for leakage and the respective repair.
- Inspect the Pipes for Clogging
If no leaks are found, clogging might be responsible for the low water pressure. Check the pipes preceding the spigot for corrosion or scale. Please note that PEX and PVC pipes rarely experience this issue.
If the spigot is clogged or likely to be clogged, one can consider replacing it. This can be achieved using a pair of adjustable pipe wrenches.
The water should be turned off at street level before replacing the outdoor faucet to avoid getting splashed.
If the new pipes look okay and the new spigot does not increase the pressure, there is a possibility that the pressure coming from the main water supply is low.
One can use a ¾ inch or ½ inch pressure test gauge to test the water pressure at the end of the spigot. It should ideally be between 45 to 55 PSI.
- Adjusting the Pressure at the Main Supply
This can be achieved if your garden spigot is connected after thew water pressure regulator. The regulator is usually located where the water supply is connected to the street.
Please note that some garden faucets are connect directly to the main supply that comes from the street and thus the pressure cannot be regulated.
The pressure regulator usually has an adjustment screw that can be adjusted to increase or decrease the pressure. Each regulator has a rating usually from 30 to 70 PSI. A clockwise turn usually results to an increase in pressure.
NB: Before increasing the pressure significantly, it is highly advisable to consult a plumber as an excessive increase in pressure is likely to strain on old pipes and result to leakages. Extreme pressure can also destroy some appliances and fixtures in the plumbing system.
Additionally, a very big drop in water pressure could be an indicator of a more serious problem that requires the attention of a professional.
From the above scientific principles, and gardening experience, it is evident that the best size garden hose for low water pressure is 3/8 inch in diameter.
By checking on garden hose size chart, you will notice that this size is smaller than most garden faucets which results to an increase in the velocity of water and the dynamic pressure of the water. It is also recommended to go for a shorter garden hose as longer hoses experience a further loss in pressure.
It is also highly recommended to check on the piping system to try and troubleshoot the low water system. This can be caused by leaks, clogging etc. Solving this can be a long-term solution.