Backwash system for swimming pool

A backwash system for a swimming pool including a pool discharge line and a return line and a filter, characterized by a forward pump in fluid communication between the pool discharge line and the filter and a reverse pump in the return line, and a strainer housing of unique construction in fluid communication between the forward pump and the pool discharge line. The strainer housing includes a strainer basket separating the strainer port from the pool discharge line and the strainer port communicating with the forward pump. A pressure-actuated valve operates within the strainer housing to open fluid communication between the pool discharge line and the strainer when the flow of liquid is in the forward direction and to close the strainer port to the pool discharge line when the flow of fluid is in the reverse direction. A waste line having a pivotal check valve is in communication with the strainer housing on the same side of the strainer basket as the pool discharge line, and the discharge check valve is adapted to be opened to discharge the contents of the strainer housing when the flow of liquid is in the reverse direction. Control means are also provided for selectively actuating the forward and reverse pumps, whereby actuation of the reverse pump automatically backwashes the filter and backwashes the strainer within the strainer housing.

BACKGROUND OF THE INVENTION 
This invention relates to a filtration system for a swimming pool, and more 
particularly to a filtration backwashing system for a swimming pool. 
Filtration systems for swimming pools including circulating means for 
backwashing the filtration system are well known in the art, as 
illustrated in the following U.S. Pat. Nos.: 
3,061,100 Fehlmann--Oct. 30, 1962 
3,220,553 Growall et al--Nov. 30, 1965 
3,420,376 Smith--Jan. 7, 1969 
3,581,895 Howard--June 1, 1971 
3,801,992 Sable--Apr. 9, 1974 
Fehlmann and Growall et al employ a single reversible pump and motor for 
reversing the circulation of swimming pool water through a filter media. 
Richards U.S. Pat. No. 25,865, issued Sept. 21, 1965, discloses a 
backwashing system for backwashing filter beds and also for removing trash 
from a strainer basket, when the circulation of liquid is reversed. 
SUMMARY OF THE INVENTION 
It is an object of this invention to provide a backwash filtration system 
for a swimming pool in which the strainer basket protecting the main pump 
is backwashed and cleared of debris simultaneously with the backwashing of 
the filter. 
It is also an object of this invention to provide a filtration backwash 
system for a swimming pool incorporating selectively operated forward and 
reverse pumps, in which the forward pump, when actuated, pumps liquid from 
the discharge line from the swimming pool through the strainer of the 
forward pump, the filter and back through the inoperative reverse pump in 
the return line to the pool. When the forward pump is de-energized, and 
the reverse pump is energized, the flow of liquid to and from the pool is 
reversed to backwash the filter and also to backwash the strainer basket 
protecting the forward pump. 
The strainer basket is mounted in a uniquely constructed strainer housing 
including ports on opposite sides of the strainer basket connecting the 
pool discharge line and the intake of the forward pump. A waste line is 
also connected to the strainer housing on the same side of the strainer 
basket as the port communicating with the pool discharge line. The waste 
line includes a check valve adapted to be opened by the reverse flow of 
liquid through the system and adapted to be closed by its own weight and 
the weight of water on the discharge side of the check valve in the waste 
line when the circulation of the system is normally forward. A 
pressure-actuated valve is slidably mounted within the port of the 
strainer housing communicating with the pool discharge line so that the 
pressure-actuated valve is normally open when the liquid is flowing in the 
forward direction. The pressure-actuated valve is closed by the reverse 
flow of water to divert the flow of water carrying waste material from the 
filter media, as well as waste material from the strainer basket, out 
through the waste line, instead of back through the pool discharge line.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawings in more detail, and more particularly to 
FIGS. 1-3, the filtration system 10 made in accordance with this invention 
includes a filter 12 of conventional construction including a filter 
housing 13 within which is supported a filter media, such as sand 14. The 
filter 12 is disclosed mounted upon a concrete base 15. When the concrete 
base 15 is formed outdoors, a housing 16 having an insulated liner 17 may 
be hinged to the base 15 by hinges 18 for concealment and protection from 
the weather. 
Liquid, specifically water, is normally pumped from the swimming pool, not 
shown, through a pool discharge line 20, forward pump strainer housing 21, 
forward, or main, pump 22, and a filter inlet line 23 into the filter 
housing 13 above the filter media 14 through inlet port 24. The forward 
pump 22 is driven by the forward pump motor 25. The pool discharge line 20 
may have a pair of branch lines, including the main drain line 26 and the 
skimmer line 27, each of which may include a manual cutoff valve 28 and 
29, respectively. After the water passes downward through the filter media 
24 in the normal forward direction, it flows through the filter outlet 
ports 30 and filter outlet line 31 and through the reverse motor 32 in 
reverse direction. The water then flows in reverse through the reverse 
motor strainer housing 33 and through pool return line 34 as fresh clean 
water, back into the swimming pool, not shown. The reverse pump 33 is 
driven by a reverse pump motor 32. 
Optionally connected to the pool return line 34 is a heater bypass line 36, 
including heater 37, bypass cutoff valves 38 and 39, and return line 
cutoff valve 40. 
The forward strainer housing 21 is of a generally cylindrical shape having 
an annular inward projecting ledge 41 upon which rests the annular rim 42 
of a conventional cylindrical strainer basket 43. A first or lower port 44 
is connected to a fluid line or pipe 45 which is connected to the intake 
of the forward pump 22. 
Formed in the upper side wall of the strainer housing 21 is a strainer port 
46 threaded receiving the pool discharge line 20. Fitted within the 
discharge line 20 and the strainer port 46 is a sleeve liner 47 adapted to 
slidably receive a pressure-actuated slide valve 48. The slide valve 48 
includes a valve head 49 having a pressure face 50 and a tubular and 
cylindrical slide element 51 slidably received within the sleeve liner 47. 
A discharge opening 52 is formed in the cylindrical wall of the slide 
element 51. 
The slide valve 48 is adapted to move reciprocally between the solid-line, 
closed position disclosed in FIG. 4 and its phantom open position within 
the valve chamber 54 of the strainer housing 21, as illustrated in FIG. 4, 
and as illustrated in solid lines in FIG. 5. The slide valve 48 moves to 
its closed position when the pressure within the valve chamber 54 is 
greater than the pressure within the pool discharge line 20. When the 
pressure in the pool discharge line 20 is greater than the pressure within 
the valve chamber 54, then the slide valve 48 is moved to its open 
position. 
Also formed in the side wall of the strainer housing 21 and communicating 
with the valve chamber 54 through the waste discharge port 55 is an 
L-shaped waste discharge conduit 56, with one leg directed upward and 
communicating with a check valve chamber 57 through a valve port 59 in the 
bottom end of the valve chamber 57. The vertical valve port 59 is adapted 
to be opened and closed by a check valve in the form of a hinged flap 
valve 60 adapted to be seated in closed position upon the annular valve 
seat 61 on top of the discharge port 59. When the flap valve 60 is open, 
water is discharged upward through valve chamber 57, and then through the 
"Harts Loop" of the waste line 58, then downward through the waste line 58 
to drain. 
Thus, when the pressure within the valve chamber 54 closes the slide valve 
48 and exceeds the weight of water within the check valve chamber 57, the 
flap valve 60 is opened upward to permit the flow of water upward and out 
through the water line 58. Such flow occurs when the circulation of water 
through the filtration system 10 is in reverse, that is when the reverse 
pump 32 is energized and the forward pump 22 is de-energized. 
Manual or automatic controls (FIG. 1) may be connected by appropriate 
electrical leads 64 and 65 to the respective forward and reverse motors 25 
and 35, respectively. 
In the operation of the filtration system 10, normally the controls 63 are 
actuated to energize the forward motor 25 in order to drive the forward 
pump 22, and to de-energize the reverse motor 35, thereby de-energizing or 
de-actuating the reverse pump 32. 
When the forward pump 22 is actuated, water is drawn from the swimming pool 
through either or both of the branch lines 26 and 27 and the pool 
discharge line 20, causing the slide valve 42 to move to its open position 
disclosed in phantom in FIG. 4 and in solid lines in FIG. 5. The water 
then passes through slide valve opening 52 and forward strainer basket 43 
for removal of trash. Accordingly trash-free water is introduced through 
the port 44 and intake line 45 into the forward pump 22. The water is then 
discharged from the pump 22 through the filter inlet line 23, inlet port 
24 into the top of the filter housing 13, where the water circulates by 
gravity through the filter media 14, such as sand. The filtered water then 
enters the filter outlet ports 30, passes through the filter outlet line 
31 and flows in reverse through the reverse motor 32 and strainer housing 
33, where the clean water is returned to the swimming pool, not shown, 
through the pool return line 34. During normal operation the return line 
valve 40 is open, and the heater line valves 38 and 39 are closed. 
However, when it is desired to heat the water returned to the swimming 
pool, the main valve 40 is closed and both cutoff valves 38 and 39 are 
opened, and the heater 37 is energized. 
When it is desired to backwash the pool water, the forward motor 25 is 
de-energized and the reverse motor 35 is energized to cut off the forward 
pump 22 and to drive the reverse pump 33. The circulation of the water is 
then completely reversed, flowing from the pool through the return line 
34, the reverse strainer housing 33, reverse motor 32, filter outlet line 
31 and discharged into the filter housing 13 through the outlet ports 30 
below the filter media 14. The water is then forced upward through the 
filter media 14 to clean the filter media 14. The dirty water then 
discharges from the filter housing 13 through the filter inlet port 24, 
filter inlet line 23 and in reverse through the idle forward pump 22. The 
dirty water then discharges in reverse through the forward pump intake 
line 45 into the bottom of the forward strainer housing 21. The upward 
force of the water entering the strainer port 44 then forces the larger 
debris upward from the strainer basket 43 into the valve chamber 54 and 
outward through the discharge port 55. Simultaneously, the upward flow of 
dirty water creates sufficient pressure against the pressure face 50 of 
the slide valve 48 to cause the slide valve 48 to move toward the right of 
FIG. 4 and to seat against the strainer port 46 to close the flow of 
liquid from the valve chamber 54 into the pool discharge line 20. 
With the pool discharge line 20 now isolated, the dirty and polluted water 
is discharged through the discharge port 55, upward through the discharge 
conduit 56 to force open the flap valve 60, and continues upward through 
the valve chamber 57 into the waste line 58. The waste water then moves 
through the waste line 58 through the upper bend or "Harts Loop" of the 
waste line 58, as disclosed in FIGS. 1 and 3, and descends by gravity to a 
drain or other point of discharge, not shown. 
It will be noted that as the water is circulated in reverse by the reverse 
pump 32, it not only backwashes the filter media 14 within the filter 12, 
but also backwashes the strainer basket 43 within the forward strainer 
housing 21, in order to remove leaves and other waste materials 
automatically from the straining housing 21. 
Although the top of the strainer housing 21 can be opened for manual 
inspection and cleaning by removing the top or lid 67, such operation is 
far less frequent with the circulation system 10 made in accordance with 
this invention, since the strainer basket 43 is automatically cleaned by 
the backwashing circulation of the water. 
It will also be noted that the construction of the slide valve 48 is such 
that the strainer port 46 is immediately closed at the wall of the 
strainer housing 21, as opposed to the employment of a check valve within 
the pool discharge line 20 remote from the strainer port 46. Thus the 
entire pool discharge line 20 is maintained in a state of cleanliness by 
its being closed at the strainer port 46. 
The wall of the check valve chamber 57 above the flap valve is provided 
with an air vent 68 to prevent siphoning in the waste line 58 and the 
valve chamber 57. 
The construction and location of the flap valve 60 permits ready opening by 
pressure and closing solely by the weight of the water above the flap 
valve 60, or by virtue of only the weight of the flap valve, without any 
additional springs or weight for its manipulation. 
In actual experiments, it has been found that when other types of check 
valves than the flap valve 60 are employed with springs or weights to bias 
the check valve to a closed position, these springs and weights provide 
too much counter-pressure, and tend to close the check valve too soon. The 
result has been that trash, and particularly leaves, released from the 
strainer basket 43 by the reverse flow causes such leaves to stick upon 
the face of the check valve thereby preventing the check valve from 
completely seating after the pressure of the reverse waste flow has 
ceased. An improperly seated waste check valve permits enough air seepage 
into the forward flow of water to create pump-priming problems. 
It has also been found that where the waste check valve is broadly in the 
form of ball valves, that is having translating movement toward and away 
from the valve port, without any swinging or hinging action, leaves also 
tend to adhere to the face of the ball check valve. 
Accordingly, it is important to have a check valve in the form of a hinged 
flap valve 60 which is mounted on top of a vertically disposed valve port, 
such as valve port 59, to permit only the weight of the water, plus the 
weight of the valve 60, to close the valve port 59. When the hinged flap 
valve 60 swings upward by virtue of the upward flow of waste water, any 
leaves or trash which might have a tendency to adhere to the face of the 
valve 60, would be immediately washed or swept off the face of the check 
valve 60 by virtue of its attitude substantially parallel to the reverse 
flow, as disclosed in FIG. 4. On the other hand, an open check valve which 
is normal to the reverse flow would tend to block the passage of trash or 
leaves long enough for the leaves to adhere to the face of the valve and 
to be held in that position by the flow of waste water normal to the plane 
of the valve. 
Separate forward and reverse pumps 22 and 32 are employed instead of a 
single reversible pump. Sometimes air is trapped in the top of the filter 
housing 13. If a single reversible pump is employed, the reversal of flow 
would cause such trapped air to be sucked back into the reversible pump 
causing the pump to lose its prime. Moreover, continued reverse pumping 
could create a partial vacuum within the top of the filter housing 13 
above the filter media 14 sufficient to collapse the walls of conventional 
filter tanks. 
Although the system 10 disclosed in the drawings would normally be mounted 
above the water level of the swimming pool, nevertheless if the platform 
15 were mounted lower, the "Harts loop" in the waste line 58, as disclosed 
in FIGS. 1 and 3 would have to be at least as high as the water level.