ᐅ Optimal Pipe Diameter for Irrigation System

Hello everyone,

we have the opportunity to have a separate water line installed directly from the main supply through the basement wall into the garden on short notice. The goal is to enable an irrigation system later on. However, there is no detailed planning for this yet, and the installation of the system itself will take place after we move in. The available garden area is over 1000m² (10,764 ft²). For now, we would only have the line installed into the garden so that splash protection and paving can be added later without obstruction.

The company is now asking us about the preferred pipe diameter and suggests 3/4 inch. Without much expertise, that seems rather small to me. A larger pipe hardly increases the cost, but what would be a sensible diameter? 1 inch?

Best regards

It would make sense to completely avoid using tap water for the garden area. Then this question doesn't arise. You can invest the money more effectively elsewhere. Otherwise, check whether there is enough pressure with a 1-inch (25mm) pipe.

Pay attention to two things: definitely have a shut-off valve installed right at the branching point in the basement! Then plan where the valves and the control system will be located later. Power supply is required there accordingly.

We have 3 circuits, all in 3/4 inch. In your case, I would lean more towards 1 inch. For you, it will probably come down to about 5 circuits.

nordanney schrieb:

It would make sense to completely avoid using tap water for the garden area. Then the question wouldn’t even arise.

And where would I get water from then?

nordanney schrieb:

Then the question doesn’t come up. You could invest the money more wisely.

Right now, it’s about an investment of maybe €200 for a measure that I wouldn’t be able to implement later. You’re probably referring to a rainwater harvesting tank; apart from the challenging excavation at our place, it would never be cost-effective. We do not pay any rainwater charges or sewage fees for garden water.

Joedreck schrieb:

Pay attention to two things: definitely have a shut-off valve installed right at the branch in the basement! Then plan where the valves and control system should be located later on. That requires power supply.

A shut-off valve with drainage is clear; the garden water meter will be installed there as well. I have electrical power in the garage with a line running out to the garden, so we can stay flexible. It will be a few meters, but that doesn’t affect the power supply. Detailed planning is difficult right now, also budget-wise. That’s why the plan was first to have the water line buried generously in a loop.

Thanks for the assessment; then we will go for a 1" pipe. We can’t influence the pressure, but this is definitely better than the outdoor faucet originally planned.

Fuchur schrieb:

And where can I get water from then?

For example, a well, cistern, etc.?

Fuchur schrieb:

Right now, it’s about an investment of maybe €200 (about $220) for a measure I won’t be able to make up for later.

They don’t care either. The dozens of cubic meters of water (so at least install a separate external water meter to save on sewage costs) will financially drain you. Better to budget a few thousand euros for a well (with a reasonable groundwater level maybe only about €800 (about $880) including the pump). Mains water is only economical on such a property if absolutely no other option is available.

Example: A simple Gardena Polo garden sprinkler (watering approximately 200 m² (2,150 sq ft) of lawn) uses about 1.2 cubic meters of water per hour at 4 bar pressure. If you have more than 1,000 m² (10,760 sq ft), that means at least 5 sprinklers = at least 6 cubic meters per hour. How much does water cost where you are? €2.00 (about $2.20) per cubic meter (probably a bit less plus meter rental)? Add flower beds, maybe a pool...
You can quickly calculate what mains water would cost you with that.

There is no groundwater (the property is on a hill), and rock is expected at 1.5-2.0m (5-6.5 feet) depth. Any deep excavation work can be extremely challenging under these conditions. We were lucky with the basement because the rising rock base starts there, and our basement floor rests directly on the rock.