AU721018B3 - Backwash collection tank - Google Patents

Description

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COMPLETE

SPECIFICATION

PETTY PATENT SWIMMING

POOL

BACKWASH COLLECTION

TANK

The following statement is a full description of this invention including the best method of performing it known to me:

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BCTPATENTRoger SimpsojN//De 1998 SWIMMING POOL BACKWASH COLLECTION TANK The invention relates to the simplification of operation, minimization of water wastage and the elimination of environmental problems when backwashing or cleaning swimming pool filters which use diatomaceous earth or sand as a filtering medium.

Although the benefits of this invention apply to both types of filters, in that it is necessary to clean or backwash them periodically, for the purposes of this description/specification, a diatomeaceous earth filter is used. Fundamental differences in design and operation are briefly outlined later in order to establish the usefullness of the invention in both cases.

For the purposes of this description/specification, all descriptions, quantities, dimensions and details herein are based on a pool of average size, i.e. 60,000 litres unless stated otherwise.

FILTRATION CYCLE The filtration cycle commences when the filter is charged with diatomaceous earth (DE) as a powder via. the skimmer box with the filter operating valve set to "filter" to coat the filter pad fabric providing a filter bed capable of filtering to microns, a very desirous condition when clear water and efficient usage of pool chemicals is required. However, as the filtration cycle continues over a period of time, the solids particles accumulating on the filter bed cause pressure build up in the filter and hence lower flow rate, hence inefficient filtering and hence the need to clear the filter pads of the accumulated solids and DE. This is accomplished by either backwashing i.e. reversing the flow of water through the filter (filter operating valve set to "backwash") to flush the DE and solids to waste (usually to shire drains or a soakwell), or dismantling the filter to manually clean the pads using a high pressure hose. The duration of this cycle is usually 1 to 3 weeks in summer, 3 to 8 weeks in winter depending on a number of factors such as pool usage and ingress of dirt and wind blown particles.

PROBLEMS ASSOCIATED WITH BACKWASIING a) Pool water contains chemicals including DE, which are potentially damaging to the environment when piping to shire drains or a soakwell. Indeed in most shire authorities it is illegal to pipe directly to shire drains (although most turn a blind eye to it possibly due to the difficulty in policing).

b) If the filter/pump is not close to the shire drain or soakwell, pressure losses due to the long discharge pipe reduce backwash pumping pressure, resulting in only a partial or fragmented disintegration of the filter bed, hence inefficient backwashing and hence the need to backwash more frequently, hence more water wastage and pollution.

BCT/PATENTRoger Simpsont/Dcc 1998 c) Ifa soakwell is employed, depending on size, it periodically needs to be dug out and the necessity to conceal such an unsightly thing from the elegant pool setting usually results in locating the soakwell in a restricted area to conceal close to fences or under shrubs making solids removal a cumbersome task.

d) Both the above waste water.

PROBLEMS ASSOCIATED WITH DISMANTLING THE FILTER TO MANUALLY CLEAN THE FILTER PADS a) As any pool owner knows keeping the filtering system sealed and airtight is vital to its efficient operation. Periodically "breaking" the filter joint, whether a bolted flange or a compression ring type joint is employed to remove the filter pads, presents a challenge in refitting and resealing properly. Joints, gaskets or "O" rings must be cleaned thoroughly, smeared with a jointing compound and reassembled carefully to ensure an airtight seal.

Even then, if the joint still leaks the procedure must be repeated.

The best policy is that once the filtering system is sealed it is best to leave it that way.

b) This method of cleaning the pads is tedious and time consuming.

The filter pads are sometimes grouped in such a way as to make cleaning with a hose difficult.

c) Hosing offpads, even carrying them to a place where they can be hosed is messy, leaving white residue stains on paths and lawns.

All the problems aforementioned, associated with the backwashing or manual cleaning of a swimming pool filter are eliminated by the use of this invention as described below and in the accompanying illustrations.

The BACKWASH COLLECTION TANK comprises a 250 litre capacity tank (item 1) of suitable height to diameter ratio, c/w integral inlet, outlet and overflow nozzles and an inside bottom flange. A filter membrane (item which is bolted to the bottom flange. A solids cake basket (item 3) of robust construction and a lid (item (Referfig. 1) All the above are from a suitable non corrosive material e.g. polyethylene or PVC. All screws or bolts from stainless steel. All nozzles to accept screwed fittings.

The unit should be installed in close proximity to the swimming pool filter and the tank bottom at least 300mm above the pool high water level.

BCT/PATENTRoger SimpsonwIme 1998 The tank inlet (50 NB) is connected directly to the filter backwash discharge with suitable screwed fittings to facilitate installation and removal. The outlet nozzle (12 NB) is piped directly back to the swimming pool, preferably to the skimmer box.

It is anticipated that due to this invention, future skimmer boxes would be fitted with a suitable fitting to accommodate this connection. If necessary, the overflow (40 NB) can be piped to a suitable low area, within eyesight of the filter backwash valve.

The backwashing operation utilizing the Backwash Collection Tank is described as follows:- The filter operating valve is switched from filter cycle fig.2) to backwash cycle (fig. 3) allowing the dirty backwash water to flow into the Backwash Collection Tank until water is seen overflowing from the overflow nozzle/pipe. The 250 litre capacity tank will allow approx. 30 seconds backwashing, enough time to ensure filter pads are thoroughly cleaned of all DE and solids before recharging the filter with fresh DE.

The dirty backwash water is filtered as it flows by gravity, through the Backwash Collection Tank filter membrane and back to the swimming pool.

As the cycle is repeated, solids and DE will accumulate to a point (approx.

of tank capacity) when it is necessary to remove the solids cake basket and dispose of them. This operation would need to be carried out every 3/4 months in the following manner.

The solids cake should be removed and emptied immediately before a backwashing to ensure that all water in the Backwash Collection Tank has drained back to the pool leaving behind the solids "cake" which is firm and easy to dispose of.

(The time taken to drain, through the filter membrane, back to the pool varies, depending on the depth of solids accumulated in the solids cake basket from subsequent backwashes) The lid is removed and the shaft of the solids cake basket is grasped firmly and rotated in a circular motion to free it from the cake. After disposal of the solids, the basket and lid are reinstalled.

SAND FILTERS DIFFERENCES IN OPERATION AND DESIGN Sand filters employ a deep bed of sand as a filtering medium, the coarser filtering capabilities (30 microns as compared to 5 microns in DE filters) being duly compensated for by a more simplistic operation and design, in that during the backwashing operation, the sand filtering medium is retained in the filter, eliminating the need to recharge the filter with medium after backwashing. However although sand filters are rarely dismantled, the necessity to backwash and deal with the water and solids still remains. In fact sand filters generally use more water in backwashing than DE filters, so whether a larger backwash tank is employed, or more frequent backwashes are performed to accomodate this demand, a Backwash Collection Tank is still an attractive and maintenance free method of dealing with backwash water.

Claims (3)

1. A BACKWASH COLLECTION TANK when operated by the method of collecting the entire backwash water volume in a single tank and filtering the said water by gravity only from the tank, through a membrane, via an outlet pipe, back to the swimming pool.

2. A BACKWASH COLLECTION TANK of claim 1 when operated by the method of manually removing and disposing of the solids cake (which is collected in a solids basket) during pool filtration, when.the accumulated solids is no greater than 20% of the capacity of the tank

3. A BACKWASH COLLECTION TANK of claim 1 comprising a tank, a filter, a olids removal vessel and a lid. ROGER SIMPSON 14 April 2000