Golf Course Drainage: Questions Greenkeepers Ask Us Most

The winter of 2023 to 2024 tested every greenkeeper in Britain.

Clubs closed for weeks at a time, and one Yorkshire course, Renishaw Park, shut for good after flood damage. With Met Office projections pointing to wetter winters and heavier downpours, drainage has become the job that decides whether members can play.

At AFT Trenchers, we have built trenching machines in Sudbury, Suffolk, for more than 50 years. Every autumn, greenkeepers call us with the same golf course drainage questions. This page answers them in one place.

If you want the bigger picture first, our guide to golf course drainage explains how the main systems work.

Where Our Answers Come From

Many of these answers build on the work of the late Geoffrey Davison, one of the first people in the world to study sportsturf drainage in depth. Geoffrey advised AFT in the days of our founder, Rodney Fulford, and kept sharing ideas informally since 2001. His thinking helped shape the Wizz Wheel 55, the Sandbander, and our sand-placement undercarriage with three levels of compaction.

Diagnosing the Problem

Why is this area of the course wet?

Usually more than one reason. Geoffrey Davison identified eight:

• Rain beyond the existing drainage capacity.
• Fine soil.
• Compaction.
• Run-off from higher ground.
• Seepage from below.
• Saucer-shaped hollows.
• Heavy wear.
• High water table.

Look at where water sits and when. A wet strip at the foot of a slope suggests run-off or seepage. A hollow on a green may only need re-shaping, with a gentle lower lip cut in to let the water out. Ground under paths and heavy traffic is usually compacted rather than poorly drained, so it needs aeration or a different surface rather than more pipes.

Often several causes act together, which is why it pays to walk the course during and after heavy rain and note exactly where water lies.

Is it a drainage problem, or am I overwatering?

Check irrigation first.

If an area is only wet after watering, look at run times and check for leaking pipes. The fix may be in the control box, not the ground.

Should I repair or replace old drains that have stopped working?

Replace them, in most cases.

Tracing faults in old drains is slow and often inconclusive. It is usually better to leave them in place and install a new, properly designed system alongside.

Design and Materials

Do I need pipes, or will sand slits do the job?

Usually both. 

Pipes are the primary system that carries water away.

Great Barr Golf Club using their AFT45 trencher for drainage 

Sand slits are the secondary system that quickly delivers water to the pipes.

Only soils with at least 75% sand drain fast on their own, so slits bypass the soil rather than trying to change it. Sand topdressing helps the surface but does not change how the soil below drains.

To turn a typical soil green into a free-draining one, you would need to import and mix in hundreds of tonnes of sand, which is rarely practical. A matrix of pipes and slits does the job without disturbing the soil that grows your grass.

How deep should fairway drains go?

As a general guide, main drains sit at least 600mm deep and laterals at least 450mm, measured to the bottom of the pipe. They go deeper where needed to keep a steady fall.

How far apart should lateral drains be?

Around 5m apart, crossed by sand or sand-and-gravel slits at about 2m. Laterals 10m apart will work, but usually too slowly for golf. Green approaches take more wear, so they need closer spacing.

If there are budget restraints, start with wider spacings, observe the results, and if needed at a later date, come in between. GPS readings would be very useful to know exact positions.

What should go in the trench, and what should cap it?

Clean, rounded pea gravel around the pipe, then at least 200mm of firmly consolidated, low-fines sand to the surface, topped off with root zone.

Never take gravel to the surface. It clogs quickly with soil, damages mowers and gets in the way of play.

Where should the water go once it is collected?

To a clear, free-flowing outlet. 

Pipes should end in rigid sections set into a headwall or an inspection chamber, not loose perforated pipe poking out of a ditch bank.

Chambers should double as silt traps and be emptied regularly.

Blocked outlets are surprisingly common and make a working system look broken.

Water From Higher Ground

How do I stop underground seepage?

Intercept it before it reaches the problem area.

Seepage does not always follow the slope you can see. Water moves through layers in the subsoil, a little like liquid weeping from between the layers of a cut onion, and it can surface a long way from where it fell, sometimes years later. It is especially common where a course was built using cut-and-fill earthworks.

1. Start by finding the source. Trial holes help show the direction and depth of the flow.
2. Once you know those, a pipe in a suitably deep, wide trench, backfilled with permeable material up to the surface, will usually catch it. Where the flow is heavy, a waterproof membrane fitted against the lower wall of the trench before backfilling stops water slipping past the drain.

Seepage is often mistaken for a failed pipe. If a patch is wet in the same place every winter and stays wet long after the rain has stopped, suspect seepage first.

How do I deal with run-off from higher ground?

Catch it before it arrives.

On bare soil, run-off cuts channels you can see. On established turf, the same flow happens, but it is hidden, so it is easy to overlook. Run-off is a common problem on parkland courses, where fairways often sit below rising or wooded ground.

First, look at the slope. Is it steep or gentle, long or short? That tells you where to intercept the water. Davison set out four options:

• A ditch, with the spoil mounded on the lower side.
• A swale, which is a shallow, wide dip that can still be mown.
• A pipe drain with permeable backfill right up to the surface.

A pipe drain laid in the bottom of a swale.

The right choice depends on the site. Where backfill reaches the surface, use gravel topped with at least 200mm of low-fines sand. Gravel alone caps quickly and causes problems for play and mowers. Expect to replace that top layer of sand from time to time.

Greens

How do I drain an existing green?

Put one or two pipes close alongside the green, not on the putting surface. Lift the turf along the slit lines, then trench sand and gravel slits about 40mm wide and 400mm deep at 1m spacings across the green towards the pipes. Backfill, relay the turf and topdress. A prepared greens team can finish a green in about two days.

About four weeks later, once the turf has knitted, finer sand slits, around 20mm wide and 150mm deep, at 250mm spacing can be cut across the first set.

The Sandbander is the ideal tool for sand slitting 

They carry surface water quickly into the larger slits. Use the same sand in both, ideally one tested to drain at 1,000mm an hour or more, so water moves freely from one to the other.

Should we rebuild greens to USGA specification instead?

Not usually. 

A rebuild is expensive, takes greens out of play for weeks or months, and only performs if built precisely to a tested specification. Many older soil greens grow better turf than imported rootzones and can be drained to a very high standard.

Designed-profile greens also tend to need more costly, attentive maintenance. Draining an existing green keeps its character, keeps it in play and costs a fraction of a rebuild.

Timing and Disruption

When is the best time of year to do the work?

When the soil is moist but firm. Timeliness is key.

For many UK courses that means early autumn or spring, but the ground, not the calendar, should decide. Working on saturated ground damages turf and haul routes, while baked ground is slow going and hard on machines.

This is one of the golf course drainage questions where owning your own trencher really helps, because you can work in short bursts whenever the ground is right instead of waiting for a contractor’s booked dates.

How long will greens be out of play?

Often a day or two, if trenches are narrow and the backfill is firmly consolidated.

Narrow trenches heal faster and need less material. Our article on careful backfilling explains why this step matters so much.

Doing the Work In-House

Should the work be done in-house or by a contractor?

It depends on scale, and it is one of the golf course drainage questions we hear most.

For large schemes, use an experienced contractor with the machinery and labour to finish on time.

For greens, approaches, wet spots and ongoing slitting, in-house work is usually more cost-effective. Contractor transport costs weigh heavily on small jobs, and your own kit lets you work when conditions are right.

Many clubs have a contractor install the main pipes, then add slits themselves.

Should we buy, hire, or hire with an operator?

It depends on how much work you have and who will do it. There are four routes:

• Contractor: usually the most expensive option, but specialists bring their own kit and experience. The contractor needs to be able to fit the work into their schedule.
• Hire the machine: worth considering if your team is trained, can be spared for days or weeks, and you already have a clear drainage plan. This could be a good short term option. But one needs to consider potentially paying for a hire machine while the weather is not appropriate for trenching.
• Hire with an operator: often cheaper than a contractor, but the club still plans and directs the work, so a senior member of staff needs to be on site throughout. Your staff are still likely to be laying the pipe, backfilling and tidying the area.
• Buy: makes sense when you have ongoing work, or when the machine will also handle irrigation and cables. A trencher also keeps a resale value. Medium term, one of the most cost-effective options. The work can be carried out at any time of the year when staffing and weather permit. Drainage work can therefore be completed gradually over time.

The break-even point is simple to work out. Add up what you would spend on hire or contractor visits over five years, then compare it with the purchase price. Remember that a well-maintained AFT trencher can run for more than 20 years.

Which trencher do I need, chain or wheel?

Both, ideally, on one machine. 

A chain digs pipe, irrigation and cable trenches. Caldy Golf Club has installed around 13,000m of drainage with theirs.

 

A slitting wheel cuts narrow drainage slits.

The compact AFT45 takes either, with a slitting wheel from 40 to 70mm wide and up to 450mm deep.

What tractor do I need, and will the trencher mark the turf?

A compact tractor with a hydrostatic or creep transmission of 30+ HP and two pairs of feed/return hydraulic spool valves will operate the AFT45. With its conveyor fitted the AFT45 weighs about 480kg, and the conveyor lifts spoil straight into a trailer, so nothing is left on the turf. It attaches to the tractor’s three-point linkage and is easy to move between holes, or between sites on a trailer.

The conveyor keeps the sides of the trench clean by putting the spoil directly onto a trailer

Can a trencher also dig irrigation and cable trenches?

Yes, and that is a big part of the case for owning one. Belton Park Golf Club, for example, uses its AFT45 for irrigation work.

How do we backfill narrow slits properly?

With a hopper that places and consolidates the material for you. Consolidating sand in a narrow slit by hand is very difficult. The AFT Dual Use Hopper backfills with gravel, sand or both using three compaction rollers, and is designed to leave playable surfaces within 24 hours. Colchester United used the same trencher, Sandbander and hopper combination on its stadium pitch.

The Dual Use Hopper at Etchinghill Golf Club can backfill with both gravel and sand

Cost and Maintenance

What does golf course drainage cost?

It depends on four things:

• Spacing: closer spacing drains faster but costs more.
• Trench width: Wide trenches need more gravel and sand. A trench cut to suit the pipe needs less gravel, less sand and less labour, and it heals faster, so holes come back into play sooner. Oversized pipes add cost without draining any faster, which is why narrow trenches save money.
• Materials: Cheap sand potentially drains slowly.
• Disruption to the course that can be accepted by members.

Doing smaller areas in-house also removes the transport charges that make contractor prices high on small jobs. But in-house work depends on staffing availability.

What is the payback in playable days or revenue?

Start by counting the days you lose now, because that is the figure a committee understands. Romford Golf Club, for example, was closed for 32 days between November and March during the wet 2023 to 2024 winter.

To build a simple case:

• Record closed days, temporary greens and buggy bans over the last two or three winters.
• Put a value on each closed day: visitor green fees, society bookings, and bar and catering takings.
• Add the less visible costs: member complaints, resignations and extra labour repairing damaged turf.
• Compare the total with the cost of the scheme, spread over its working life.

Targeted work on the worst greens and approaches usually wins back the most days for the least money, so that is often the best place to start.

How long does slit drainage last?

Years, not forever. 

Fine particles gradually clog the sand near the surface. Cutting fresh sand slits across the old ones, roughly every two years on greens, reconnects the surface to the system beneath. Budget for this from the start.

Does aeration help drainage?

Yes, if it creates space in the soil.

Machines that remove cores or gently lift the surface help, used several times a year. Tines that only push soil aside do little, because they compress the soil around each hole.

What routine maintenance does a drainage system need?

Less than most clubs fear, but it must be regular.

Far more systems fail through neglect than through poor design. A simple routine covers most of it:

• Walk the outlets after heavy rain and keep them clear of silt, debris and vegetation.
• Empty the silt traps in inspection chambers as part of the regular calendar.
• Fit vermin guards on outlets, and keep tree and shrub roots away from pipe runs.
• Note new wet patches as soon as they appear, as they often point to a blockage.
• Aerate several times a year, when the ground is neither too wet nor too hard, at the machine’s recommended speed.
• Top up any sunken slits with matching sand.
• Keep a drawn record of where every pipe and slit runs. It saves time and avoids damage the next time you dig.

The One Question to Ask Before Any Other

If there is a single thread through every answer above, it is this: find out why the ground is wet before you spend a penny fixing it.

From there, the principles are simple, and timeliness is key:

• Check outlets first. A blocked outfall can make a sound system fail.
• Catch water from higher ground before it arrives, whether it runs over the surface or seeps underneath.
• Bypass the soil. Pipes and sand-capped slits work together.
• Drain before you rebuild. Existing greens can be improved in days, not months.
• Own the timing. Light, compact kit lets your team work when conditions are right.
• Plan for renewal. Drainage is a system to maintain, not a one-off job.

Got a golf course drainage question we have not answered? We are always happy to talk it through. Tell us about your course, your soil and your team, and we will point you towards the right approach.