25mm Black Underground Pipe

Product details

25mm Black Irrigation Pipe is designed to run underground to invisibly connect the irrigation system together. The irrigation pipe may be used to run from the water supply to the valve box or from the valve box to popup sprinklers or to connect between flower beds.

To comply with the UK Water Regulations, irrigation pipe is coloured black to ensure that it can be easily differentiated from drinking water pipe, which will always use blue underground pipe.

For strength and durability underground the irrigation pipe is manufactured using either Medium Density Polyethylene (MDPE) or High Density Polyethylene (HDPE) pipe. This has a thick pipe wall to prevent crushing and damage when buried underground.  In private gardens we recommend the pipe is buried at least 300m underground and on construction sites we would recommend the black irrigation pipe is buried underground at least 500mm.

Medium-density polyethylene (MDPE) pipes are versatile and widely used for various underground applications. These pipes are specifically engineered to withstand the harsh conditions and demanding requirements of buried installations. Their key uses underground include:

1. Water Supply: Blue MDPE pipes are commonly used for underground water supply networks. Their resistance to corrosion and durability make them an ideal choice for safely transporting potable water to homes, businesses, and communities.

2. Gas Distribution: Yellow MDPE pipes are extensively employed for underground natural gas distribution systems. Their strength and leak-resistant properties ensure the safe and reliable delivery of gas to residential and commercial properties.

3. Irrigation: Black 25mm diameter MDPE pipes serve as the backbone of buried irrigation systems. Their flexibility and resistance to root intrusion make them well-suited for efficiently delivering water to horticultural and agricultural fields and landscape irrigation systems.

MDPE pipes are favoured for underground applications due to their exceptional performance, longevity, and ability to withstand the challenges of buried environments, ensuring reliable services for water, gas, electricity, and more.

Use compression fittings to connect the 25mm Black Irrigation Pipe

How much water can 25mm irrigation pipe carry?

The amount of water that can pass through 25mm irrigation pipe depends mainly on the length of the pipe and the number of outlets along it. As the pipe gets longer, friction causes more pressure loss, so the recommended maximum flow reduces.

If there are several outlets spaced along the pipe, water leaves the pipe progressively rather than the full flow travelling all the way to the end. This means a pipe supplying several evenly spaced outlets can carry a higher combined flow than a pipe supplying a single outlet at the end.

Use the table below as a simple design guide. The figures show the maximum recommended total flow in litres per hour for 25mm MDPE pipe.

Number of outlets	25m pipe	50m pipe	100m pipe	200m pipe
1	1,300 l/hr	910 l/hr	625 l/hr	430 l/hr
2	1,650 l/hr	1,150 l/hr	800 l/hr	545 l/hr
3	1,875 l/hr	1,275 l/hr	875 l/hr	600 l/hr
4	1,950 l/hr	1,345 l/hr	925 l/hr	635 l/hr
5	2,000 l/hr	1,390 l/hr	955 l/hr	655 l/hr
6	2,050 l/hr	1,415 l/hr	980 l/hr	675 l/hr
7	2,050 l/hr	1,415 l/hr	980 l/hr	675 l/hr
8	2,050 l/hr	1,415 l/hr	980 l/hr	675 l/hr

Example: If you have 100m of 25mm pipe supplying four evenly spaced outlets, aim to keep the combined flow through those outlets to around 925 litres per hour or less.

Check how much water your supply can provide

The figures in the table show how much water the pipe can carry, but the available water supply can also limit the flow through the irrigation system.

As a general rule of thumb, a typical outside garden tap may provide around 600 to 800 litres per hour, although the actual flow can vary considerably depending on the property, water pressure and pipework.

This means that even though 25mm pipe may be capable of carrying considerably more water, a garden tap supplying 700 litres per hour will still limit the irrigation system to approximately 700 litres per hour.

A pumped water supply can provide substantially more flow. For example, our Category 5 pump units will generally provide around 2,500 to 4,000 litres per hour, depending on the pressure required by the irrigation system.

When using a higher-flow pumped supply, the pipe size becomes increasingly important. If the pump can supply more water than the 25mm pipe can carry at the required length, a larger pipe size may be needed to avoid excessive pressure loss.

Maximum usable flow = the lower of the water supply flow or the pipe capacity.

What do we mean by an outlet?

An outlet is a point where water leaves the main 25mm pipe. This might be a connection to a sprinkler, a branch pipe or another part of the irrigation system. The figures in the table refer to the combined flow from all of the outlets, not the flow available from each individual outlet.

How have these figures been calculated?

The table is intended as a practical guide for selecting irrigation pipe sizes. The figures are based on:

• 12 bar MDPE pipe
• Level ground
• Outlets evenly spaced along the pipe
• A maximum pressure loss through the pipe of approximately 0.2 bar
• A maximum water velocity of 1.7m/s

If the pipe runs significantly uphill, the outlets are concentrated towards the end of the pipe, or your irrigation system requires a particularly high flow, a larger pipe size may be required.

Technical specification:

Outside diameter: 25mm
Pressure rating: 10 bar
Pipe colour: Black
Wall thickness: 2.4mm.

Available in 25M, 50M or 100M coils.