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Thread: Static Pressure Drop After Pump Shuts Off

  1. #1

    Question Static Pressure Drop After Pump Shuts Off

    Just installed a new bladder tank on my home system. I have adjusted the pressure switch for cut in a 40 psi and shut off ~ 62 psi. Inline on the 1" supply line I have a flow control valve, the pressure switch, a GE large capacity whole house filter, and last the tank. The pump cuts in and off at the exact settings, but immediately after shut off, the gage pressure drops back down to the 50's. Could it be that the filter is restricting the real pressure that the switch is seeing? If so should I adjust the switch up until a higher static pressure is realized, or replace the filter with a less restrictive one. (I had a paper type filter until this downtime, and replaced it with a carbon type filter which I believe is more restrictive.)

  2. #2
    In the Trades Bob NH's Avatar
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    Quote Originally Posted by SC Handyman
    Just installed a new bladder tank on my home system. I have adjusted the pressure switch for cut in a 40 psi and shut off ~ 62 psi. Inline on the 1" supply line I have a flow control valve, the pressure switch, a GE large capacity whole house filter, and last the tank. The pump cuts in and off at the exact settings, but immediately after shut off, the gage pressure drops back down to the 50's. Could it be that the filter is restricting the real pressure that the switch is seeing? If so should I adjust the switch up until a higher static pressure is realized, or replace the filter with a less restrictive one. (I had a paper type filter until this downtime, and replaced it with a carbon type filter which I believe is more restrictive.)
    You should put the pressure connection to the switch at the tank. If the switch is mounted on the pump, you can run a tube from somewhere at the tank to the switch, or you can move the switch itself to where it measures the tank pressure and run wire from the switch to the pump.

    If you have a submersible pump you should have a pressure relief valve on the inlet side of the filter. If you have a shallow well jet pump you don't need a relief valve if the pressure capability of the pump is less than the pressure rating of the filter.

    You need to pay a lot of attention to the pressure drop across the filter and you should have a gauge on both inlet and outlet of the filter.

  3. #3

    Smile

    Thanks for the quick reply! It is a submersed system, ~ 350'. I guess a picture would be good here. I got the part about the added gauge, and the PRV valve makes sense. If I add the PRV, what should the relief pressure be set at? Will it act to relieve the diff. in PSI each time the pump cycles? If so, where will the water go. My system is in my basement.

  4. #4
    In the Trades Bob NH's Avatar
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    Quote Originally Posted by SC Handyman
    Thanks for the quick reply! It is a submersed system, ~ 350'. I guess a picture would be good here. I got the part about the added gauge, and the PRV valve makes sense. If I add the PRV, what should the relief pressure be set at? Will it act to relieve the diff. in PSI each time the pump cycles? If so, where will the water go. My system is in my basement.
    The relief valve is installed in a tee on the inlet side of the filter, with the discharge going to a safe place.

    A 75 psi preset Pressure Relief Valve is pretty standard and inexpensive but may be marginal for the 62 psi shutoff. You might want to get one that you can set at 85 to 90 if your pump and filter will handle the pressure. You want to allow use of the maximum pressure drop across the filter before you have to change it.

    The relief valve should NEVER relieve if you change the filters at the correct interval. However, you should pipe the outlet to a safe place without a shutoff valve anywhere in the relief valve line.

    You will save a lot of the cost of filter cartridges if you put a second unit in parallel. The time between changes will increase by a factor of 3 or more and the annual cost of cartridges will be less than 2/3 of what you will pay with only one filter unit.

    What does the carbon filter remove? If you are in an area with radon in the water, activated carbon will remove radon. It will also technically become radioactive waste when it gets full. http://www.uri.edu/ce/wq/has/PDFs/Ca...t_revision.pdf

    http://www.epa.gov/radiation/radionu...htm#properties

    It is mostly low energy alpha radiation so if you collect it in a plastic bag and dispose of it in a safe place you will be OK.

  5. #5

    Cool

    Many Thanks! There is no problem with the increase in psi. I actually needed a little more to overcome the low tap pressure upstairs. I don't think we have a radon problem here, but that's something I didn't know about the radioactivity.

  6. #6
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    As much as I dislike these highly overated so called "Whole House Filters", if you must have one. Install it after the pump, tank, switch, gauge etc. That's where it belongs.

    bob...

  7. #7

    Thumbs up

    Sorry "whole house" filters offend you. I guess that name was given to them by the GE marketing group. I had a lot of silt and sand in my water before. The pump is down about 300' and hasn't been pulled for over 12 years. I have the filter installed after everything but the tank because I wanted to keep the pressure drop to a minimum beyond the tank. So far (for the past 5-6 years) it has given no problems and I feel better about keep all the silt and sand out of my system.

  8. #8
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    It's not the filter that offends me as much as how they are marketed at the Big Box stores.

    If you still have sand and silt coming into the house, they are at least better than nothing.

    If you don't still have sand and silt, I would get rid of it.

    bob...

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