Seaflo 33 & 42 series diaphragm pump start the thermal protection device when the motor temperature reaches 125℃.

Turn on the power supply, open the water switch, the pressure switch senses the water pressure is less than the stop pressure to start the start water pump; turn off the water switch, the pressure switch induction water pressure reaches the stop pressure break circuit, the water pump stop working.

The actual water flow of the waterway is less than the water flow of the water pump. The by-pass switch is started, and part of the water flow circulates internally and releases the pressure, to prevent the pressure switch from starting frequently.

The working principle is different. The function of the pressure switch is to automatically break the switch when the pump reaches the set pressure value, and the pump stops working. The function of the by-pass switch is that when the pressure in the pump reaches the maximum value, the by-pass switch can make the water in the pump circulate, stop pumping but the water in the pump will also circulate, need to turn off the power pump to stop.

The opening flow rate is unadjustable, but can be customized.

The best mounting position for Seaflo diaphragm pump is placed horizontally. If installed vertically, pump head down to prevent water flow into the motor. The diaphragm pump can be mounted upside down without affecting the pressure and flow rate.

The noise of the 51 diaphragm pump is 70DB and its life-span is 1,000 hours.

Seaflo series of pumps have been tested for 24-hour life and can continuously work for 24 hours.

O-ring, we generally do EPDM (used for marine & RV sector) and VITON (used for chemical liquid-agricultural industry). The NBR material can be customized, with MOQ: 1,000 sets per order.

Intermittent work is because there is a temperature control protection in the pump, which stops when the temperature reaches a certain value and works after cooling. Continuity work does not install temperature control protection, such as Seaflo 31 series pump, because the motor temperature is not high, do not need to add thermal protection switch, can work continuously.

No, it can dry run for a short time (about 3 minutes). Seaflo pump uses a pressure switch and only stops working when the pressure value reaches the critical point. Or cut off the power from the outside.

Seaflo 21 series diaphragm pumps have a maximum withstand liquid temperature of 60℃.

The life-span of Seaflo 21 series motor is about 600 hours, diaphragm life is about 1000 hours, 31 series motor is about 800 hours, diaphragm life is about 800 hours; 41 series motor is about 800 hours, diaphragm life is about 800 hours.

The 3-4-5 chamber diaphragm pump motors all last between 800 and 1000 hours, and the diaphragm life between 800 and 1000 hours.

1. 21 series

a. Doesn’t turn on 

i. Verify wiring is correct:  black to negative, red to positive 

ii. Verify power source voltage and cranking capacity

iii. Pressure switch 

To see if the pressure switch works, connect both wires from the back of the motor to a power source. You will have to disconnect one wire from the pressure switch to do this

iv. Bump motor with rubber mallet 

b. Doesn’t pump water 

i. Verify the hose isn’t clogged 

ii. Verify if the diaphragm is punctured/use a strainer

iii. Verify it has access to water 

iv. Verify that connecting ports are sealed and not admitting air

v. Priming ability of 4 feet suction lift 

c. Leaks 

i. Tighten screws in pump head 

d. Want to change pressure 

i. Please note that use outside of factory settings may cause a void to the warranty of the pump. On the pump head, there is an allen screw sticking out of the pressure switch. Turn this screw clockwise to increase the cutoff pressure, and counterclockwise to decrease the cutoff pressure. Please note that this pressure you are changing is the cutout pressure, not the leading pressure provided by the pump. 

e. Fitting size: ⅜” hose barb 

f. No check valve 

2. 22 series

a. Doesn’t turn on 

i. Verify wiring is correct:  black to negative, red to positive 

ii. Verify power source voltage and cranking capacity

iii. Pressure switch 

To see if the pressure switch works, connect both wires from the back of the motor to a power source. You will have to disconnect one wire from the pressure switch to do this.

iv. Bump motor with rubber mallet 

b. Doesn’t pump water 

i. Verify the hose isn’t clogged

ii. Verify if the diaphragm is punctured/use a strainer

iii. Verify it has access to water

iv. Verify that connecting ports are sealed and not admitting air

v. Priming ability of 4 feet suction lift

c. Leaks

i. Tighten screws in pump head

d. Want to change pressure

i. Please note that use outside of factory settings may cause a void to the warranty of the pump. On the pump head, there is an allen screw sticking out of the pressure switch. Turn this screw clockwise to increase the cutoff pressure, and counterclockwise to decrease the cutoff pressure. Please note that this pressure you are changing is the cutout pressure, not the leading pressure provided by the pump. 

e. Bypass 

i. The bypass is mechanism by which water is recycled from the pressurized side to the depressurized side of the pump. This smooths flow and reduces cycling. To adjust the bypass, find the allen screw sticking out of the circular nub on the pump head that is not the pressure switch screw. Turn this screw clockwise to increase the bypass pressure, and counterclockwise to decrease the bypass pressure. Please not that if the pressure on the bypass is too high, it will effectively be deactivated, and if the pressure is too low relative to the cutoff pressure of the pressure switch, it will not allow the pump to turn off. We suggest that the bypass setting only be adjusted by professionals.

f. Fitting size: ⅜” hose barb 

g. No check valve 

3. 31/35 series

a. Doesn’t turn on 

i. Verify wiring is correct:  black to negative, red to positive 

ii. Verify power source voltage and cranking capacity

iii. Pressure switch 

To see if the pressure switch works, connect both wires from the back of the motor to a power source. You will have to disconnect one wire from the pressure switch to do this. 

iv. Bump motor with rubber mallet 

b. Doesn’t pump water 

i. Verify the hose isn’t clogged 

ii. Verify if the diaphragm is punctured/use a strainer

iii. Verify it has access to water 

iv. Verify that connecting ports are sealed and not admitting air

v. Priming ability of 6 feet suction lift 

c. Leaks

i. Tighten screws in pump head

ii. The customer may remove the pump head to inspect the inside by removing the pump head anchoring screws

iii. Customer must use strainer supplied with the pump. If not, it can cause punctures to the diaphragm

d. Want to change pressure 

i. Please note that use outside of factory settings may cause a void to the warranty of the pump. On the pump head, there is an allen screw sticking out of the pressure switch. Turn this screw clockwise to increase the cutoff pressure, and counterclockwise to decrease the cutoff pressure. Please note that this pressure you are changing is the cutout pressure, not the leading pressure provided by the pump. 

e. Fitting size:

i. 31

1. Pump: ½” FNPS

2. Comes with (2) ½” FNPS to ⅜” hose barb

ii. 35

1. Pump: ⅝” snap-in port

2. Comes with (2) ⅝” snap-in port to ⅜” hose barb

f. Has built in check valve 

4. 33 series / 34 series

a. Doesn’t turn on 

i. Verify wiring is correct:  black to negative, red to positive 

ii. Verify power source voltage and cranking capacity

iii. Pressure switch

1. To see if the pressure switch works, connect both wires from the back of the motor to a power source. You will have to disconnect one wire from the pressure switch to do this. 

iv. Bump motor with rubber mallet 

b. Doesn’t pump water 

i. Verify the hose isn’t clogged

ii. Verify if the diaphragm is punctured/use a strainer

iii. Verify it has access to water

iv. Verify that connecting ports are sealed and not admitting air

v. Priming ability of 6 feet suction lift 

c. Leaks

i. Tighten screws in pump head 

ii. The customer may remove the pump head to inspect the inside by removing the pump head anchoring screws

iii. Customer must use strainer supplied with the pump. If not, it can cause punctures to the diaphragm

d. Want to change pressure 

i. Please note that use outside of factory settings may cause a void to the warranty of the pump. On the pump head, there is an allen screw sticking out of the pressure switch. Turn this screw clockwise to increase the cutoff pressure, and counterclockwise to decrease the cutoff pressure. Please note that this pressure you are changing is the cutout pressure, not the leading pressure provided by the pump. 

e. Fitting size:

i. Pump: ½” MNPS

ii. Comes with (2) ½” FNPS - ½” hose barb

f. Has built in check valve

5. 41 series

a. Doesn’t turn on 

i. Verify wiring is correct:  black to negative, red to positive 

ii. Verify power source voltage and cranking capacity

iii. Pressure switch 

To see if the pressure switch works, connect both wires from the back of the motor to a power source. You will have to disconnect one wire from the pressure switch to do this. 

iv. Bump motor with rubber mallet 

b. Doesn’t pump water 

i. Verify the hose isn’t clogged 

ii. Verify if the diaphragm is punctured/use a strainer

iii. Verify it has access to water 

iv. Verify that connecting ports are sealed and not admitting air

v. Priming ability of 6 feet suction lift

c. Leaks

i. Tighten screws in pump head 

ii. The customer may remove the pump head to inspect the inside by removing the pump head anchoring screws 

iii. Customer must use strainer supplied with the pump. If not, it can cause punctures to the diaphragm

d. Want to change pressure 

i. Please note that use outside of factory settings may cause a void to the warranty of the pump. On the pump head, there is an allen screw sticking out of the pressure switch. Turn this screw clockwise to increase the cutoff pressure, and counterclockwise to decrease the cutoff pressure. Please note that this pressure you are changing is the cutout pressure, not the leading pressure provided by the pump. 

e. Fitting size:

i. Pump: ⅝” snap-in port

ii. Comes with (2) ⅝” snap-in port to ⅜” hose barb

f. Has built in check valve 

6. 42/43 series

a. Doesn’t turn on 

i. Verify wiring is correct:  black to negative, red to positive 

ii. Verify power source voltage and cranking capacity

iii. Pressure switch 

To see if the pressure switch works, connect both wires from the back of the motor to a power source. You will have to disconnect one wire from the pressure switch to do this.

iv. Bump motor with rubber mallet 

b. Doesn’t pump water 

i. Verify the hose isn’t clogged 

ii. Verify if the diaphragm is punctured/use a strainer

iii. Verify it has access to water 

iv. Verify that connecting ports are sealed and not admitting air

v. Priming ability of 6 feet suction lift 

c. Leaks

i. Tighten screws in pump head 

ii. The customer may remove the pump head to inspect the inside by removing the pump head anchoring screws 

iii. Customer must use strainer supplied with the pump. If not, it can cause punctures to the diaphragm

d. Want to change pressure 

i. Please note that use outside of factory settings may cause a void to the warranty of the pump. On the pump head, there is an allen screw sticking out of the pressure switch. Turn this screw clockwise to increase the cutoff pressure, and counterclockwise to decrease the cutoff pressure. Please note that this pressure you are changing is the cutout pressure, not the leading pressure provided by the pump. 

e. Bypass 

i. The bypass is mechanism by which water is recycled from the pressurized side to the depressurized side of the pump. This smooths flow and reduces cycling. To adjust the bypass, find the allen screw sticking out of the circular nub on the pump head that is not the pressure switch screw. Turn this screw clockwise to increase the bypass pressure, and counterclockwise to decrease the bypass pressure. Please not that if the pressure on the bypass is too high, it will effectively be deactivated, and if the pressure is too low relative to the cutoff pressure of the pressure switch, it will not allow the pump to turn off. We suggest that the bypass setting only be adjusted by professionals.

f. Fitting size:

i. 42

1. Pump: ½” FNPS

2. Comes with (2) ½” FNPS to ⅜” hose barb

ii. 43

1. Pump: ⅝” snap-in port

2. Comes with (2) ⅝” snap-in port to ⅜” hose barb

g. Has built in check valve 

7. 51/52 series

a. Doesn’t turn on 

i. Verify wiring is correct:  black to negative, red to positive 

ii. Verify power source voltage and cranking capacity

iii. Pressure switch 

To see if the pressure switch works, connect both wires from the back of the motor to a power source. You will have to disconnect one wire from the pressure switch to do this. 

iv. Bump motor with rubber mallet 

b. Doesn’t pump water 

i. Verify the hose isn’t clogged 

ii. Verify if the diaphragm is punctured/use a strainer

iii. Verify it has access to water

iv. Verify that connecting ports are sealed and not admitting air

v. Priming ability of 6 feet suction lift 

c. Leaks

i. Tighten screws in pump head 

ii. The customer may remove the pump head to inspect the inside by removing the pump head anchoring screws 

iii. Customer must use strainer supplied with the pump. If not, it can cause punctures to the diaphragm

d. Want to change pressure 

i. Please note that use outside of factory settings may cause a void to the warranty of the pump. On the pump head, there is an allen screw sticking out of the pressure switch. Turn this screw clockwise to increase the cutoff pressure, and counterclockwise to decrease the cutoff pressure. Please note that this pressure you are changing is the cutout pressure, not the leading pressure provided by the pump. 

e. Fitting size:

i. 51

1. Pump: ½” FNPS

2. Comes with (2) ½” FNPS to ⅜” hose barb

ii. 52

1. Pump: ⅝” snap-in port

2. Comes with (2) ⅝” snap-in port to ⅜” hose barb

iii. Both have optional connectors available to purchase which adapt to ¾” hose barb 

8. 53 series

a. Doesn’t turn on

i. Verify wiring is correct:  black to negative, red to positive 

ii. Verify power source voltage and cranking capacity

iii. Pressure switch 

To see if the pressure switch works, connect both wires from the back of the motor to a power source. You will have to disconnect one wire from the pressure switch to do this.

iv. Bump motor with rubber mallet 

b. Doesn’t pump water 

i. Verify the hose isn’t clogged 

ii. Verify if the diaphragm is punctured/use a strainer

iii. Verify it has access to water 

iv. Verify that connecting ports are sealed and not admitting air

v. Priming ability of 6 feet suction lift 

c. Leaks

i. Tighten screws in pump head 

ii. The customer may remove the pump head to inspect the inside by removing the pump head anchoring screws 

iii. Customer must use strainer supplied with the pump. If not, it can cause punctures to the diaphragm

d. Want to change pressure 

i. Please note that use outside of factory settings may cause a void to the warranty of the pump. On the pump head, there is an allen screw sticking out of the pressure switch. Turn this screw clockwise to increase the cutoff pressure, and counterclockwise to decrease the cutoff pressure. Please note that this pressure you are changing is the cutout pressure, not the leading pressure provided by the pump. 

e. Bypass

i. The bypass is mechanism by which water is recycled from the pressurized side to the depressurized side of the pump. This smooths flow and reduces cycling. To adjust the bypass, find the allen screw sticking out of the circular nub on the pump head that is not the pressure switch screw. Turn this screw clockwise to increase the bypass pressure, and counterclockwise to decrease the bypass pressure. Please not that if the pressure on the bypass is too high, it will effectively be deactivated, and if the pressure is too low relative to the cutoff pressure of the pressure switch, it will not allow the pump to turn off. We suggest that the bypass setting only be adjusted by professionals.

f. Relay

i. The pressure switch is protected by an external mechanical relay. If damage occurs to this, the pump will not shut off.

g. Fitting size:

i. New version

1. Pump: ½” FNPS

2. Comes with (2) ½” FNPS to ⅜” hose barb

ii. Old version

1. Pump: ⅝” snap-in port

2. Comes with (2) ⅝” snap-in port to ⅜” hose barb

iii. Both have optional connectors available to purchase which adapt to ¾” hose barb

9. 54 / 55 series

a. Doesn’t turn on 

i. Verify wiring is correct:  black to negative, red to positive 

ii. Verify power source voltage and cranking capacity

iii. Pressure switch 

1. To see if the pressure switch works, connect both wires from the back of the motor to a power source. You will have to disconnect one wire from the pressure switch to do this.

iv. Bump motor with rubber mallet 

b. Doesn’t pump water 

i. Verify the hose isn’t clogged 

ii. Verify if the diaphragm is punctured/use a strainer

iii. Verify it has access to water 

iv. Verify that connecting ports are sealed and not admitting air

v. Priming ability of 6 feet suction lift 

c. Leaks

i. Tighten screws in pump head 

ii. The customer may remove the pump head to inspect the inside by removing the pump head anchoring screws 

iii. Customer must use strainer supplied with the pump. If not, it can cause punctures to the diaphragm

d. Want to change pressure 

i. Please note that use outside of factory settings may cause a void to the warranty of the pump. On the pump head, there is an allen screw sticking out of the pressure switch. Turn this screw clockwise to increase the cutoff pressure, and counterclockwise to decrease the cutoff pressure. Please note that this pressure you are changing is the cutout pressure, not the leading pressure provided by the pump. 

e. Bypass 

i. The bypass is mechanism by which water is recycled from the pressurized side to the depressurized side of the pump. This smooths flow and reduces cycling. To adjust the bypass, find the allen screw sticking out of the circular nub on the pump head that is not the pressure switch screw. Turn this screw clockwise to increase the bypass pressure, and counterclockwise to decrease the bypass pressure. Please not that if the pressure on the bypass is too high, it will effectively be deactivated, and if the pressure is too low relative to the cutoff pressure of the pressure switch, it will not allow the pump to turn off. We suggest that the bypass setting only be adjusted by professionals.

f. Fitting size:

i. New version

1. Pump: ½” FNPS

2. Comes with (2) ½” FNPS to ⅜” hose barb

3. Both have optional connectors available to purchase which adapt to ¾” hose barb

Don't worry. 
Fresh water pumps have to  be 100% bested before leaving SEAFLO factory.
Our quality control team undertake a hydrostatic test for each pump.
Thus, there is residual water in our new pump head.  

The check valve prevents back flow from the outlet of the pump back into the water tank. Check valves are rated from 200PSI – 250PSI.