Constant pressure system with air venturi iron filter

Discussion in 'Pumps and Tanks Well Forum & Blog. Water is life.' started by steve604, Jun 4, 2015.

  1. steve604

    steve604 New Member

    Joined:
    May 20, 2015
    Occupation:
    Electrician
    Location:
    Aldergrove British Columbia
    I currently have a fairly new constant pressure system in my house that works great but I have iron/manganese issues. I installed one of the air venturi iron filter systems (Rainfresh brand) fully knowing it wouldn't work properly but I really like the idea of not using chemicals in the system.

    What I'm seeing now is, the air venturi pulls in air like it's supposed to under high water demand. The well pump runs at a constant speed and all is well. When running something like the shower alone, the pump doesn't seem to have a minimum speed low enough to run constantly so it's ramping up and down every 4 or 5 seconds and the venturi sucks air every time the pump ramps up. It also looks like the filter media tank is acting as a small pressure tank.

    I'm thinking that I will get a small compressor and connect that to the venturi with an electric solenoid that will turn on anytime the well pump runs. That will constantly inject no matter what the flow rate of the pump is. Can I just adapt an air line to the inlet nozzle on the venturi?

    And then to cure the short cycling of the pump (which I'm told isn't actually a problem for a variable speed pump) I could add a big pressure tank to the system. I know that this is actually defeating the principle behind the constant pressure system but I had no idea that iron and manganese were going to be such a problem with my new well until I was actually getting water out of it. I'm actually contemplating bypassing the whole system and just running the existing pump off of a standard pressure switch with a big tank. I've read about a few people doing this anyway due to multiple failures of the Grundfos controller. If I do this, I wouldn't have to worry about adding a compressor to the system either.
     
  2. valveman

    valveman Cary Austin Staff Member

    Joined:
    Mar 15, 2006
    Occupation:
    Pump Controls Technician
    Location:
    Lubbock, Texas
    That is not the way a Grundfos variable speed system should work. It should not be cycling on and off while you use something small like a shower. It is designed to slow down the motor so it keeps running steady when using small amounts of water. When it is cycling on and off that usually means the CU301 controller is no longer in communication with the electronics in the motor. This is a very common problem with those units. They use the same wire that feeds power to the motor to communicate a radio signal to the controller, and this doesn't work very well. So when the motor and controller are not communicating, it reverts to acting like a pressure switch with 15 PSI between on/off and just keeps doing that. The newer models will actually do that I believe 1000 times before giving a fault that says "lost communication". You are having a problem and it just hasn't told you yet.

    That pump will run fine using a standard pressure switch instead of the CU301 controller. But you either need to use a much larger pressure tank to slow down the cycling, or you can use a CSV with any size tank (even the small one) to make it a real constant pressure system without varying the speed of the motor and having all the problems that go with.

    Yes I think you could add an air compressor to the air intake on the venturi. Just make sure it is an "oil less" compressor. But you might look into the "Sulfur Eliminator". It dumps 1.5 gallons per hour of aerated water down the well and gets rid of the problem before water is ever pumped to the surface.
     
    steve604 likes this.
  3. Sponsor

    Sponsor Paid Advertisement

     
    steve604 likes this.
  4. steve604

    steve604 New Member

    Joined:
    May 20, 2015
    Occupation:
    Electrician
    Location:
    Aldergrove British Columbia
    thanks for the reply. I did some experimenting today with the shower running and the pump controller does the 15 psi cycling while the air venturi is pulling air. if i crank down the adjustment in the venturi so it stops working, the pump holds a constant pressure like it should.

    i installed the venturi ahead of the control system like the instructions said and i believe it's pushing air bubbles to the sensor which is confusing the control so it goes into trouble mode. it looks like moving the venturi to a point past the controls might cure my problems but it will likely stop the venturi from working. if that's the case, i may have no choice but to add a compressor to the system.

    what sort of pressure will open up the venturi to allow air to enter? will it even work this way? i'll play with it again tomorrow as this might actually be unnecessary if the venturi still does it's thing normally most of the time.

    thanks for your time
     
  5. valveman

    valveman Cary Austin Staff Member

    Joined:
    Mar 15, 2006
    Occupation:
    Pump Controls Technician
    Location:
    Lubbock, Texas
    If you move the sensor and get the pump to run steady while small amounts of water are being used, it will eliminate the pressure differential you need to make the venturi work. If you add a compressor to the system, it will just need to produce more pressure than is in the water line to be able to force air into the system.
     
  6. steve604

    steve604 New Member

    Joined:
    May 20, 2015
    Occupation:
    Electrician
    Location:
    Aldergrove British Columbia
    I got it working. I hooked up a compressor with an electric air solenoid running off of a relay connected to the aux output terminals of the grundfos controller. I have the regulator turned down right down. Any time the pump runs, a small amount of air is injected into the venturi. It's not perfect and I'll probably have to play with it a little along the way but it's worth it considering the benefits of having iron free water.

    I still need to install a check valve ahead of the veturi to keep air from backing up into my untreated water but other than that I hear water pouring through air space in the birm filter tank which I'm pretty sure is the main principle of operation for the iron filter.
     

    Attached Files:

  7. valveman

    valveman Cary Austin Staff Member

    Joined:
    Mar 15, 2006
    Occupation:
    Pump Controls Technician
    Location:
    Lubbock, Texas
    There is already a check valve on the pump. Neither water nor air can go backwards. You should not need an additional check valve.
     
  8. steve604

    steve604 New Member

    Joined:
    May 20, 2015
    Occupation:
    Electrician
    Location:
    Aldergrove British Columbia
    I have a unfiltered exterior hose bib that seems to be pulling air from the birm filter tank. I figured i would put the check valve in between the filter and hose bib
     
  9. LLigetfa

    LLigetfa DIYer, not in the trades

    Joined:
    Feb 6, 2011
    Occupation:
    Semi-Retired
    Location:
    NW Ontario, Canada
    My guess is that the hose bib isn't actually "pulling" air from the tank, just that some of the entrained air is getting separated en-route and collecting at the bib.

    There should be a checkvalve (backflow preventer, actually) so that contaminated water from the hose cannot flow back into the house. Obviously that would not stop air from going out to the bib.
     
  10. steve604

    steve604 New Member

    Joined:
    May 20, 2015
    Occupation:
    Electrician
    Location:
    Aldergrove British Columbia
    I can hear the air gurgling up from the birm tank and the hose bib will spit air/water for a while until there is no air left in the tank. I'll mount the check valve right on the tank inlet which should fix that.

    Water from the hose should never flow backwards unless the pump is shut down and the hose bib is turned on and it somehow siphons it's way back. It would be some rare occurrence while the system is shut down to be worked on.
     
  11. steve604

    steve604 New Member

    Joined:
    May 20, 2015
    Occupation:
    Electrician
    Location:
    Aldergrove British Columbia
    The check valave fixed the air bubbles in my pre-filtered water bib. I can definitely smell the H2S odour from that tap now. Nothing but fresh water in the house now. I shouldn't have any more fuxture staining happening either. I have milky looking water issues but that is minor compared to the smells and staining i had before this.

    I was skeptical about the air injection system due to reading a few posts where people said it was a joke and doesn't work. Seems to work pretty good in my opinion.
     
Similar Threads: Constant pressure
Forum Title Date
Pumps and Tanks Well Forum & Blog. Water is life. Constant pressure pump issues Apr 1, 2019
Pumps and Tanks Well Forum & Blog. Water is life. Well Pump Constantly Running, Low Pressure, Bladder Tank Not Filling Mar 3, 2019
Pumps and Tanks Well Forum & Blog. Water is life. Loud click/thud, then loss of water pressure - need to reset (Constant Pressure System) Jul 21, 2018
Pumps and Tanks Well Forum & Blog. Water is life. Constant pressure Grundfos system question Dec 3, 2017
Pumps and Tanks Well Forum & Blog. Water is life. Replacing constant pressure controllers Sep 5, 2017

Share This Page