Water is great to have in the garden; provided it is kept where you want it. Wherever you have water, you need waterproof membranes to keep it in.
When is water a problem?
When it leaks from ponds, pipes, downpipes, guttering, drains, tanks or anything else intended to hold it.
When it makes the ground wet and slippery.
When it makes the soil too wet for plant growth.
When it causes things to rust or rot.
WHAT NEEDS TO BE WATERPROOFED IN THE BACKYARD?
Roofs (greenhouses, garden sheds, car port, gazebo, summer house)
Roof gardens (eg. on a veranda)
Pots and their bases
Pressurised water needs more thought!
Water in taps, water pipes or chemical spray units is under pressure –and more prone to leaks than in any other situation.
Materials for waterproofing
Asphalt, Bitumen Emulsion
Washers/plumbers tape (for leaky taps/pipes)
Clay liners such as Bentonite
How to fix a leaky tap
The most common cause of a leaky tap is a worn or faulty washer. To replace a washer:
Turn off the water at the mains
Empty the water still left in the pipes into a bucket. (Don’t waste water!)
Using a plumber’s spanner, remove the top off the tap to expose the washer.
Remove and replace the washer.
Refit the top of the tap and turn the water back on at the mains.
The next most likely cause is leaks occurring through the thread that joins the different parts of the tap. This problem can be solved by dismantling the tap and winding teflon tape (plumber’s tape) around the thread before reassembling the tap. You can buy plumbers tape at most hardware stores.
How to seal a leaking pipe
Small holes or split seams in a metal or plastic pipe can be sealed with silicone. This is easily applied using a silicone gun, available from any hardware store.
Larger holes can be filled using fibreglass. Simply lay sheets of fibreglass over the hole and coat with fibreglass resin. Continue to lay extra sheets until the hole is adequately covered.
How to fix a leaking pond
A leaking garden pond can be a real headache. To find the source of the problem, you will first have to drain the pond entirely and look hard to find any cracks or holes. You make need to get down on hands and knees and run your fingers across the pond surface.
Vinyl liners can be heat-welded back together, but this usually has to be done in a factory. You can patch small holes in a vinyl liner.
Concrete ponds may develop leaks due to cracking of the concrete or inadequate sealing at installation. Prevention is the best cure – make sure you use a plastic film or other waterproofing agent when you install the pond. If the pond develops cracks, fill them with a sealant (ask an expert at a hardware store for the best product for your job).
Leaky copper pipes
The great thing about copper is that it doesn’t rust. However, it can still be bent out of shape so badly that leaks occur. In this situation, it is best to replace the damaged length of pipe. If you don’t have experience in working with copper pipe, it is best to call in an expert.
Fixing spray unit/sprayer leaks
Because small spray units hold liquid under pressure, leaks can be a problem (especially if the leaking sprayer contains herbicide or pesticide). Most split seams and puncture holes can be fixed with silicone sealant.
Wet areas next to taps can be made a lot safer by putting rubber matting down.
If a patch of lawn is getting slippery through too much walking over, consider setting stepping stones through that area. A stone or concrete surface will dry out much faster than grass.
Butyl pond liners are heavy duty, flexible water proof sheets. They can be used to line a leaky pond or create a new one.
If you are laying a concrete slab; lay plastic sheeting under the concrete to stop water seeping up from the ground underneath. This is particularly important in very wet or shaded locations; or if the slab is to be used for flooring in a shed, gazebo or other building.
Use concrete or plastic cell systems or open weave fabrics to reduce surfaces becoming muddy and slippery. You can spread either gravel or turf over the top of such systems, and they stop the surface becoming wet and slippery.
Plumbers Tape (white) can be used to patch a leaky tap at little expense
Steps can be very dangerous if they get slippery. These concrete steps have actually had a drain shaped into one side to help take excess water away.
Concrete can be slippery if the surface is smooth and wet. A simple and attractive solution is to cover it with pebbles.
Tools can be dangerous if they become slippery. Rubber handles (as on these secateurs) give good grip in all types of weather.
Remove Excess Water with Better Drainage
Too much water lying on the garden or on the lawn can create all sorts of problems. Aside from making it unpleasant to walk on the lawn, weeds and diseases can flourish and plants will find it hard to get the oxygen they need.
If you have a waterlogging problem in your garden during winter, then you will need to take steps to take the water away from the site.
WHAT TO DO?
The first thing is to observe how and where the water collects in your garden.
Does the water flow from higher parts of the garden and collect in low spots?
Does rainwater percolate into the soil or does it just lay on top?
Are some parts of the garden more prone to waterlogging than others?
Once you have done this, it is a good idea to dig a hole in the problem areas to find out about the properties of the soil. In some cases the reason the water can not drain away is because the topsoil is a thick clay that can only absorb small amounts of water at a time. In other places the subsoil might not be able to absorb water as quickly as the topsoil.
When you have identified where and why the problems are occurring, you can start remedying the situation.
There are number of ways to improve soil drainage:
By cultivating the soil to break up clay pans. This method has some short term benefits, but it can sometimes make matters worse and will not solve the problem of water ponding in low lying spots.
By adding sand, organic matter or gypsum to the soil. These solutions are really only practical when you are starting a new garden.
Making grooves or holes in the soil and filling the gaps with sand. This can improve garden soil over the long term, but it is time consuming and may damage plant roots.
The best solution to most garden drainage problems is to install a drainage system.
FIRST DECISION: SUB SURFACE OR SURFACE DRAINAGE
There are two basic types of garden drains – those that move water along the soil surface and those that move it underground. Deciding which one to use will depend upon the waterlogging problem in your garden.
If you have a problem with water moving from higher parts of the garden into lower areas, then the answer could be a spoon drain that redirects the water away from the lower part of the garden. If you have a lawn that is slippery or soggy during winter because of a heavy subsoil, then the answer might be a sub-surface agricultural drain.
WHAT IS A SPOON DRAIN?
A spoon drain is a channel cut into the soil surface. Excess water runs along the soil surface to an outlet point. One advantage of a spoon drain is that it can be made to look like a natural part of the landscape. This can be done by growing a lawn or by filling the drain with a bed of pebbles or stones.
WHAT IS AN ‘AGI’ DRAIN?
Sub-surface drains can be made from clay pipes or even fibreglass. However, for most domestic situations, the best method is to install either flexible corrugated plastic or rigid PVC agricultural (agi) pipes. Set in a bed of gravel, the water enters these pipes through slits and then flows down the slope to an outlet point.
TYPES OF SUBSURFACE DRAINS
Clay Pipes rigid, covered with stones, long lasting, water soaks through porous pipe and between joins, joins can sometimes become blocked with soil
Fibreglass Strip Drain flexible, stones are optional, water permeates through outer case, relatively new product, so durability is unknown
Corrugated Plastic flexible, covered with stones, water comes through slits in the pipe, slits can become blocked with soil, plastic can break down after a number of years
PVC – rigid, covered with stones, water enters through holes in the plastic, long lasting
THE WATER OUTLET
Any drain must go to a dispersal point. To be effective, this has to be at the lowest part of the drainage system. Before entering a storm water system, drainage water should pass through a holding pit. In some cases, you will need a plumber to connect your drain to the storm water system.
If it is impossible to find an outlet for the drainage water, there are still things you can do:
Turn the problem to your advantage by installing a pond or other water feature to collect the water.
Pump the water from the outlet to a suitable disposal point.
Create a soakaway pit a large deep hole filled with porous material such as sand or stones that collects the water and then slowly disperses it into the surrounding soil.
Whether above or below the ground, a drain should never have a slope of less than 1:200. For example, if the drain is twenty metres long, the outlet point should be at least 10cm lower than the top of the drain.
The slope of a drain should be uniform. Sharp bends should be avoided. On relatively level sites it will be difficult to create a suitable slope with a spoon drain and a sub-surface drain will have to be installed.
LAYOUT OF DRAINS
Herringbone lateral drains feed from 2 sides into a central main drain. This system has the advantage of minimizing the depth of some of the drains. If there is likely to be any subsidence after construction, laterals should be kept at less than 30m in length. On undisturbed ground, lengths up to 90m are acceptable.
Grid has laterals all running into one main drain from one side. This is less complicated, has less joins, and the main drain can run along the boundary (minimizing interference with the main parts of the garden).
LAYING AN AGI DRAIN
The drain is laid as follows....
Dig the trench (with an even slope on the base)
Lay a base of gravel or crushed rock or scoria (particle size should be between 10 and 25mm)
Lay drainage pipes in the trench
Cover pipes with the crushed rock
Place a layer of sand over the coarse material to fill within a few centimetres of the top of the trench
Cover the sand with a well draining topsoil
DISTANCE BETWEEN DRAINAGE PIPES
In heavy clay 3 to 5 metres might be necessary
In average soils, 6 9 metre spacings are adequate
In wet spots, it may be necessary to add additional pipes
DEPTH OF DRAINS
There is no firm rule, although 600mm is usually considered reasonable. If cultivation or other types of digging might be carried out in the future, it is advisable to place drains deeper (ie: 750mm)