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Testing Drainage

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troduction  

Stoppers 

 Air Test  

Water Test  

Pipelines  

Hs and ICs  

Smoke  

 Mandrel  

Repairs  

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IntroductionAll newly-laid drainage, including manholes, inspection chambers and the like, should be

tested for water-tightness prior to backfilling, as detailed in BS 8301(Code of Practice forBuilding Drainage) and BS 8005 (Guide to new sewer construction)*. Under site conditions,a test is applied in the presence of a Building Control Officer or Resident Engineer once a

section of drainage is completed, although the contractor/pipe-layer will normally undertakea test prior to the official inspection or during actual construction to ensure the drainage will

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pass; there's nothing more infuriating than having your work condemned as sub-standard!

During the construction of larger sewers, we would typically air-test a pipeline after every

second pipe length is laid. We find this make identifying problem joints or defective pipesmuch simpler and less time-consuming than it would be to undertake a single test on

completion of a full pipe run.

* These British Standards are in the process of being replaced by new European Standards, although the actual proceduresand methodology are not likely to change. Basically, it's just another bit of bureaucracy to keep the desk-pilots in Brusselsfeel as though they are earning their bread! The new standard for testing will be BS EN 1610:1998 Construction and Testingof Drains and Sewers. 

There are two basic tests; the air test and the water test. Usually, an air test is carried out topipework while a water test will only normally be required to verify a failed air test or to testmanholes/inspection chambers. Failure during an air test is NOT sufficient reason to

condemn a pipeline. If an air test indicates a leak in the system, a water test must be thenundertaken to verify and quantify the problem.

Prior to any test, the pipeline should be visually inspected for any obvious signs of damageor leakage. Mortar-jointed systems should be left for at least 48 hours before instigating anytest, to give the mortar a chance to set.

Tests are normally applied to a pipeline between consecutive manholes. Short branches

connected to the main run are usually tested as part of the main run unless they can beeasily isolated for individual testing. Manholes/IC's are tested seperately using the watertest.

StoppersBoth the air test and the water test rely on the use of expandingstoppers, also known as 'bungs'. These stoppers consist of a pair of metal plates sandwiching a flexible rubber mid-section all of which is

mounted along a hollow shaft. A large winged nut is fitted on top of themetal plates onto the threaded portion of the shaft and used to adjustthe compression of the rubber mid-section. The top of the hollow shaftmay be fitted with an end cap to form an fluid-tight seal, or with a

nipple for connecting to a manometer.

Drain Stopper

Stopper diameter is

The inside of the pipe should be cleaned before fitting thestopper, to ensure no grit or other detritus is present that couldimpair the air-tight seal required for an effective test. Thestopper is opened out to reduce the diameter of the rubber mid-section, before being squarely placed within the bore of the pipeand the screw mechanism gradually tightened, compressing the

rubber mid-section, forcing it outwards, and pressing it againstthe wall of the pipe to form a tight seal.

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increased/decreased by adjustingwing nut

Air TestingThe kit used to conduct an air-test is fairly basic andavailable from most Builders' and/or Contractors'

Merchants. It consists of a number of stoppers, ahose nipple, a length of flexible hose and amanometer (a simple U-shaped pressure gauge). A

small squeezy hand-pump with a control valve isoften included, and this is connected to the mainhose via a T-piece. The stoppers are placed in theopen ends and branches of the section of pipeline to

be tested and adjusted via the screw mechanism sothat they expand within the bore of the pipe,effecting an air-tight seal.

One stopper, normally at the head of the run, isfitted with the nipple that connects to the flexible

hose which, in turn, is connected to the manometer,which has been part-filled with water.

Kit for air test

Air is pumped into the pipeline, usually via a hand-pump with a control valve, until thereading on the manometer is around 125-150mm. The set-up is then left for 5-10 minutes toallow for temperature stabilisation within the pipe before the pressure is reduced to exactly100mm on the manometer scale.

Idealised air test set-up

The manometer is then monitoredfor a period of 5 minutes; the level of 

water in the manometer should notfall below the 75mm mark duringthis period. This is deemed to be a'pass' and the pipeline is declared

satisfactory and can be backfilled.

However, if the level in themanometer does fall below the

75mm mark, then the equipmentshould be checked and cleaned andthe pipeline examined for leaks ordefects. If any problems are

identified, they should be rectifiedbefore re-testing. If the air test isre-applied and is failed for a secondtime, a water test should beadministered.

The air test is considered to be more sensitive than a water test. Failure of an air test is

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often caused by temperature fluctuation within the pipeline caused, for example, by anuncovered pipeline being occasionally shaded by passing clouds on a sunny day. A drop intemperature of just 1°C within the pipe is sufficient to cause a drop in pressure large enoughfor the test to fail.

Water testA water test is not as strict as an air test, but is far more useful in identifying any leaks orbad joints that are causing the pipeline to fail the test, and is preferred to an air test bysome authorities. However, an air test can be set up in a matter of seconds and dismantledwithout affecting the work, making it the preferred test of the pipe layer, whereas a water

test can take 2 hours or more to establish, and is less convenient as an ongoing check forwater-tightness of newly installed pipework.

Water-testing a pipeline

A head of water is created and the pipeline examined for tell-tales signs of leakage.Following a period of settlement and acclimatisation, the level of water in the head is

monitored for a specified period and the loss of water measured and checked. It is notunknown for a pipeline that has failed an air test to pass a water test.

The size of pipe being tested will determine the test parameters. Pipes of 300mm diameter

or less follow the requirements of BS8301 (1.5m head at high end; max 4m head at lowerend) while larger diameter pipes (>=400mm) follow BS8005 (1.2m head at high end; max6m head at lower end). These requirements are summarised in the table opposite. Where apipeline would generate a head greater than that specified, it should be tested in stages, toreduce the maximum head, and minimise the risk of damage to the pipeline.

Set-up for water test on pipeline

PipeDia

100-400mm

400-750mm

Test to BS8301 BS8005

Tophead

1500mm 1200mm

MaxHead

4000mm 6000mm

Test parameters forpipelinewater test 

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The lower end and all open branches of the pipeline to be testedare stoppered as described above. A 90° bend is added to the topend of the run and a vertical pipe of the same diameter added.This vertical pipe should be braced by lashing it to a stake orsimilar, as depicted.

Water is added to the pipeline (via a hose) up to the required

head level in the vertical pipe and the pipeline visually inspectedfor leaks. The water is left to stand for at least 120 minutes, toallow for displacement of trapped air and any absorption by thepipe, before being topped up to exactly the required level.

Water test set-up

The set-up is then monitored for a period of 30 minutes, during

which the water level of the head is topped-up as required atregular intervals and the quantity of water added is recorded.After 30 minutes the total quantity of water added to the vertical

pipe during the monitoring period is calculated and can bechecked against the table opposite - read off the figure given formaximum acceptable loss for the diameter of pipe underconsideration, and multiply that by the length of pipeline beingtested. The measured quantity must be LESS than the calculatedquantity for the pipeline to pass the test.

Alternatively, the maximum acceptable loss can be calculatedas...

maximum permissible loss = 1 litre per hour per linear metre of pipeline, per metre of internal pipe diameter

...so, for a 75 metre run of 150mm pipe, the maximumpermissible loss of water during the 30 minute test would be...

1 litre/hr × 75m × 0.15m = 11.25 litres per hour = 5.6 litresduring 30 minute test period.

Acceptable water loss

Pipe Dia[mm]

Max lossper metrein 30 mins

[litres]

100 0.05

150 0.08

225 0.11

300 0.15

400 0.20

450 0.23

500 0.25

600 0.30

750 0.38

>750 seek advice

Water testing a Manhole or Inspection Chamber

Manholes and Inspection Chambers are tested in a manner similar to that outlined above. All

inlets and the outlet of the MH/IC are stoppered and the chamber filled with water to within300mm of the soffit. After a period of acclimatisation (60-120 minutes), the water level inthe chamber is visually monitored for 30 minutes.

Acceptable water loss can be calculated on the same basis as that for pipework, althoughmost tests look for a water loss of less than 25mm over a 10 minute period.

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Smoke testingAlthough testing with smoke is not an official test of water-tightness, it may be used with

non-PVCu pipelines to identify leaks or defects that have not made themselves apparent inair or water tests. Some smoke canisters can damage PVCu systems, and so, if smoke is tobe used within a PVCu system, it is essential a safe type is used. Check with themanufacturers before undertaking a smoke test.

Mandrel testing

This is a less common test, used on critical pipelines to verify the quality of installation. Amandrel is a ball or elliptical plug-shaped object that is passed through a pipeline to ensurethat the minimum acceptable internal diameter is maintained throughout. A mandrel istypically 10mm smaller in diameter than the specified minimum diamter of the pipeline

being tested, so, for a 150mm pipeline, a 135mm diameter mandrel would be used.

With flexible pipelines (PVCu) there is a degree of unavoidable deformation due to

backfilling, and so the mandrel diameter is determined as being 10mm less than 95% of thepipe internal diameter. So, for a 150mm PVCu pipeline, the mandrel would be....

150 × 95% = 142.5mm - 10mm = 132.5mm 

Making RepairsShould a pipeline or chamber fail both an air test and a water test, then the leak/defectmust be sought out and rectified before any backfilling work is undertaken. Someleaks/defects are easily identified; they may be heard to hiss as air escapes, or wetting thesuspect section with soapy water may reveal tell-tale bubbling when air pressure is raised

inside the pipe. Often, the fault can be identified as a single joint needing to be re-made or afaulty section of pipe to be replaced; other problems can be much more difficult to pinpointand may need the pipeline to be dismantled one pipe length at a time and re-tested usingthe air test until the defective joint/pipe is located.

With MHs and ICs, the most common cause of failure is a leaking chamber section joint

which can often be repaired by cutting out defective mortar/sealant and re-pointing/re-sealing as required. In some cases, it is the base of the chamber itself that is the source of the problem, often a bad seal between a pipe and the concrete surround or the base section

of a pre-formed unit. Such problems may be solved with an epoxy mortar or similar, if theexact source can be identified, although in the worst cases, the only effective cure is acomplete rebuild.

Once the fault(s) has been rectified, a further air and/or water test should be undertaken to

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ensure no further faults are present; it is not unknown for pipelines/chambers to have morethan one leak!

Other drainage pageso  Introduction

o  Draining Pavements

o  Foul or Storm? Identifying your system

o  Laying Drainage

o  Connecting Additional Drainage

o  - Inserting a new IC - Case Study

o  Manholes and Inspection Chambers

o  Gullies and Gratings

o  Testing Drains

o o  Land Drainage for Fields and Gardens

o  - Installing Land Drainage

o  Soakawayso o  Linear Drainage Systems

o  - Installing Aco Drive Drain

o  Fin Drains and Composites

o o  Written Specification

o  Manufacturers and Suppliers Links

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