EVOLUTION OF THE MOTOR CESSPOOL EMPTIER.
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How a Public Service, Fraught with Difficulties, Which in the Past Has Not Been Well Performed, is Now Thoroughly Carried Out by Motor Power.
IT WILL .come at a surprise to many people, in these days of efficient drainage schemes embracing the whole country, to learn that such things as cesspools, or dumbwells, as they are sometimes called, exist. In fact, there are ninny who do not know what the word " cesspool " means, or, at the best, have only a vague idea about it, and imagine that such things have long since been relegated to the limbo of the past, but there are many people with whom the cesspools are an everpresent problem and a continual source of trouble and expense.
Generally speaking, the cesspool is a hole sunk in the ground, usually about 4 ft. in diameter and from 10 ft. to 25 ft. deep, into wbich the waste water from the house is drained. These have to be periodically emptied, otherwise they will overflow and cause what is officially known as an "r offence."
Methods of Emptying Usually Employed.
In some eases the emptying is done by a chain pump permanently fixed in position, the contents being deposited by a wooden trough into the garden, but this can only be carried out in a very few cases, owing to the offensive smell which it creates. The general practice is to use a band-operated diaphragm punkt), Mounted Dil four wheels, which is brought to the top of the dumbwell ;' the Contents are drawn up and C58'
forced through a length of hose to a horse-drawit tank standing on the roadway. When full, the tank is taken to a neighbouring field, the emptying valve opened, and the load deposited.
In districts where a large number of cesspools exist the local council itself tarries out the work of emptying and disposal, employing a permanent staff of men, horses and vehicles for the purpose. This is a slow method, however, and causes dissatisfaction, owing to the unpleasant smell and the filth left on the pathways. etc.
During the last two or three years many councils who are burdened with this type of drainage have gone into the question of laying down a water-carriage system and establishing sewage works, but the majority of them have had to abandon the idea for the time being, owing to the excessive cost, which would seriously affect the already inflated rates. As an alternative, they have turned their attention to the selfcontained motor vacuum tank wagon, which has now reached a state of high efficiency..
Greater Economy in Operating Costs.
These motor cesspool emptiers, of which a large tiumbe-i are now being used throughout the country, work On hygienic lines, and show an enormous saving over Operation by horse
drawn vehicles. Below are given a description and illustration of a 750-gallon model manufactured by the well-known Guildford firm of Dennis Brothers, Ltd., who have turned out many of the vehicles of this class at present in operation. .
The outfit consists of a cylindrical tank, mounted at a slight angle on a standard 3i-ton chassis. A raised neck manhole is placed at the forward end a the tank, with which is incorporated a large bail valve, which seats itself in an adapter at the end of the air .pipe, connecting the tank to the pump. A 4-in, gunmetal-faced quick-acting .filling valve is situated at the rear end, a steel pipe being carried from it to the inside of the manhole. The pump is of the rotary turbo type, manufactured by Reavell and Co., Ltd., of Ipswich. It is fitted with an automatic lubricator, a springloaded valve being opened by vacuum when the machine is in operation.
The primary drive is by a sliding pinion in a special cover fitted to the road gearbox, operated by a lever in the driver's cab. A shaft fitted to this pinion transmits the drive by an
enclosed silent chain and pillion to the pump. On the side of the pump is a two-way valve, the movement of which causes the pump to he instantaneously turned from an exhauster into a compressor. This valve has four flanges, which are connected .by pipes to both ports of the pump, the tank and the silencer of the engine.
On each side of the tank is situated a suitable board for carrying up to a
total length of 300 ft. of hose. The hose is constructed of rubber, heavily armoured to ensure a long life, the internal diameter being 33 ins, It is in 12-ft. (i-in, lengths, and is easily carried by two men. A metal bell-mouth is screwed on to the length lowered into the pit, to assist the entry of the sludge into it, other lengths being screwed together and conilacted to the filling valve. The work of connecting up the hose is facilitated by the use of round-thread couplings, which also have the advantage ef a longer life than those of the V-thread type.
The Mode of Operation,
Before commencing operations, the two-way valve is placed in the " Fill" position, the air being drawn from the tank through the pump and passed into the silencer of the engine, where the obnoxious fumes from the sewage are burnt with the exhaust gas from the engine. The exhaust pipe is carried up at. the rear. of the cab so that no offebce whatever is caused.
To comuienee filling, the driver puts the pump into gear and accelerates the engine. A special governor incorporated in the induction pipe allows it to run only at a predetermined speed while driving the former. The efficiency of the pump is very high, it being capable of obtaining 20 ins. of vacuum in the tank in .1 ithn. 20 secs. Consequently, the filling valve can he opened directly the engine is started, the liquid almost inanediately flowing into the tank. The Compound pressure and vacuum gauge situated at the rear of the cab enables the Operator to see at a glance what is happening, a glass gauge also showing the amount of liquid in the tank. When the tank is nearly full the ball valve lifts and closes the entry to the air pipe, thereby preventing the pump from exhausting any more air from the tank. This is an excellent feature, as the risk of liquid entering the punip, with subsequent damage, is eliminated. The average time for filling is 4 to 10 minutes, depending on the lift and the length of hose laid out. The top of the fillingvalve is always above the level of the liquid, so,that, should the engine for any reason stop running, the contents will,iaot flow back again into the cesspool.
So soon as the filling operation is finished the driver turns the two-way-valve lever through 90 degrees. In this position the pump delivers air to the space inside the top of the tank. On the filling valve at the rear being closed, the pressure rapidly rises, the safety valve en the pipe line lifting when it reaches 15 lb. per sq. in. The driver then opens a quick-acting filling valve, compressed air passing through the hose, thoroughly cleansing it.
Another and very useful service is carried out by the compressed air at the same time—i.e., stir ring up the solid matter at the bottom of the pit, rendering it more suitable for suction. Hand-operated diaphragm pumps can only take out the water from. cesspools, the solid matter: being left. Consequently, in places where • motor vehicles have been put in commission, as much as 6 ft. to 8 ft. of sludge has been found in the pits, the accumulation of many years. Several charges of compressed air thoroughly stir this up with the liquid, facilitating the work of removal. In this way the cesspools are completely emptied, so that a longer period now elapses before they have to be emptied again.
After the completion of the cycle of
operations in emptying a cesspool the hose is disconnected from the tank and the vehicle driven to the place of discharge, usually a field or a piece of waste land in an lad:tiled place. In most cases, the original leather or canvas hose used with the horse-drawn vehicles is brought into service when emptying. Three or four 50-ft. lengths are coupled together and fixed to the emptying valve situated at the bottom of the machine, which stands on the road. The pump is run as a compressor, forcing the load out under pressure. This is an asset, as it can be deposited on high ground, if necessary, as shown in one of the accompanying illustrations.
Lifting Soil from Great Depths.
Normally, a machine can empty a cesspool to a depth of 25 ft., but, if a small U-shaped pipe is fitted to the end of the suction hose, with one end open to the atmosphere, allowing a certain quantity of air to pass up the suction pipe, it is possible to get down to 32 ft. One of these machines, with two men, can do as much work at was formerly done by 5 men, 6 horses and 3 vans. Where the cost by the old method was £1,200, the work it now done for £700, including depreciation, interest on capital,
etc. • As will he noticed from the foregoing article, the machine has been designed to carry out the work in as efficient and hygienic a manner. as possible, at the same time being simple , in operation, once again demarAtrating the superiority of the mechanically propelled vehicle over the horse-drawn type.