Frequently Asked Questions

The list of frequently asked questions provides a quick answer about common Delavan products. It intents to offer a general overview, and a reference knowledge to check first before needing to contact Technical Support.

Diaphragm Pumps

  • My pump does not turn on
    1. Check for power (Supply voltage +/- 10%)
    2. Check pressure switch. Please see ESR-008.
    3. Check relay – It will make a click sound if failed. (FB2/FB3 series demand pump)
    4. Replace motor
  • My pump is not flowing
    1. Check valve. Please see ESR-002.
    2. Check for inlet leak like a broken hose, fitting or loose hose clamp preventing the pump from priming. May need a new pump head. Please see ESR-003.
    3. If the pump is still not flowing, replace the lower housing and/or valve plate. Please see ESR-003.
  • My pump is not shutting off or does not build pressure
    1. Check for correct voltage (Supply voltage +/- 10%)
    2. Check for system debris, leaks, trapped air.
    3. Check for low flow. Replace the Lower Housing Assembly. Please see ESR-003.
    4. Check for pump head leaks (tighten screws or new pump head)
    5. Adjust pressure switch. Please see ESR-001.
  • My pump is turning on and off quickly (Cycling)

    Pump ‘cycling’ is when the pressure switch of any demand style pump is rapidly turning on and off. Understanding why your pump is doing this is essential to finding a solution to the issue.

    • Understanding Pressure Switches

    To understand why your pump is cycling it is important to understand how a pressure switch works.  On the top of all demand style pumps there is a pressure switch. Inside the pressure switch is a small diaphragm connected to an electrical On/Off switch. Once the pressure in the pump head reaches a certain pre-set limit (ex. 60 psi) the diaphragm will inflate and hit the electrical On/Off switch turning your pump off. Once the pressure in the pump goes below the pre-set limit (ex. 60 psi) the diaphragm will deflate turning the pump back on.

    • Flow vs. Restriction

    The flow of your Delavan Pump and your system’s restrictions are the next factors to consider. The flow of your Delavan Pump is written on the label of your pump. For this example, you have a 5 GPM Delavan pump and have it hooked up to nozzles or a spray wand. The nozzle or wand is only able to put 2 GPM, this is the restriction of your system. Your pump always wants to push 5 GPM but the system restriction won’t allow it. This causes your pump’s pressure switch to rapidly turn On/Off. Much like any electrical system, turning your pump On/Off rapidly is causing damage and may cause your pump to prematurely break down.

    • How do I stop my pump from cycling?

    Recognize what is causing the restriction. It could be the size of your nozzles, the wand you are using, a kinked hose in your system, the diameter of the hose, too many 90º fittings. It can be one or a few of these issues. Fixing the restriction and increasing the flow of your system will stop cycling.

    If you are using a Sprayer or Wand type system you can easily add a return to tank or “bypass” which will circulate any extra fluid back to the tank. Do this by adding a T-fitting and valve just past the outlet and a hose which will direct any excess flow back to the tank.  We have a Youtube video explaining this; https://www.youtube.com/watch?v=QEN6AXZrAGM

    Finally, you can adjust the pressure of where your pressure switch will turn off power to your pump by adjusting the set-screw on top. Follow this link for an explanation of how to do that. Please see ESR-001.

  • My pump leaks
    1. Check for loose screws at switch or pump head.
    2. Check the switch diaphragm ruptured or pinched. Replace the pressure switch. Please see ESR-008.
    3. Check for fluid in the pump head. If present, replace the lower housing assembly. Please see ESR-003.
    4. If you have a 7822FS serial number and the pump is leaking from the Flex-Ports please see Please see ESR-027.
    5.    or this youtube video. https://youtu.be/jVeK0pmCcdo

  • Why does my pump get very hot?

    It is recommended to continuously run the pumps at a pressure less than 50 PSI. If the motor is getting hot, typically the pressure is high causing the motor to work harder. Reduce the pressure to 30-40psi.

    If possible when running pumps at pressures higher than 60PSI, use the pump 50 minutes on and 10 minutes off to let pump cool down.

  • Fittings List
    MODEL STANDARD AVAILABLE OPTION
    5800 1/2″ NPT
    5900 3/4″ Quick Attach
    7800 5/8″ Quick Attach 3/8″ NPT
    7800 FLEX 3/4″ Quick Attach 5/8″ Quick Attach (Needs QA Adapter FA-7822FS)
    7870/7871 FB 1/2″ NPT
    7970 3/4″ Quick Attach
  • Import vs Domestic Pump

    Any pump with an ‘-I’ at the end of the model number is an import pump. The upper housing assembly and valve plater are not replaceable with a standard domestic pump. Pressure switches are interchangeable on all models and so are lower housing assemblies.

  • Demand vs Bypass

    A demand pump shuts off at pressure setting. You can identify a demand pump by the wire leads out of the pump head (pressure switch). A bypass pump runs continuously when it has power. You can identify a bypass pump since they only have 2 wires out of the motor.

  • Are Delavan diaphraphm pumps self priming? Can they run dry?

    Diaphragm pumps self prime and can run dry.

  • Which models are potable water safe (NSF)?

    All models are NSF certified except import and FB3 (7871/7971) series pumps.

  • Fuse/Wire Size
  • Chemical Compatibility

    Please contact Delavan Techincal Support to discuss your application.

  • Can I adjust my pressure switch?

    Adjusting the pressure switch may increase pump wear and tear which therefore reduces pump life.

  • What does Extreme Duty mean?

    Extreme Duty pumps are made with stronger and heavier duty Geolast diaphragms. Pumps with Geolast diaphragm exhibits enhanced oil-resistance and low oil swell making it ideal for oil based applications. Geolast provides moderate flex life and good abrasion resistance over a wide temperature. Should not be used with gasoline.

  • Can I pump diesel through my pump?

    Never pump gasoline, flammable liquids or combustible liquids. Pumps with santoprene diaphragms are designed for use with water-based products only. Pumps with Extreme Diaphragm (ED) designation are made with Geolast Diaphragms and are compatible with non-flammable and non-combustible oil-based liquids.

  • Can I pump bleach in my pump?

    Yes, you can pump bleach through your pump.

    Sodium hypochlorite or bleach is a key component in thousands of production and disinfection processes in a variety of industries. Though testing we have found that sodium hypochlorite does affect the elastomers (or elasticity) of the pumps diaphragm over time. Simply put, a pumps diaphragm is similar to an elastic band and continuous use over time with bleach will cause it to dry out and have less elasticity.

    There are steps you can take to prolong the life of a diaphragm pump used in conjunction with bleach.
    1. Flush out you pump after each use with fresh water for 90 Seconds
    2. Dilute the bleach. Delavan recommends a concentration of 12%. (Similar to the concentration used in most soft wash applications)
    3. Replace the pump’s diaphragm every 12-18 months (depending on usage) or when you begin to see a significant drop in flow.



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