Pressure Pump for rainwater/toilet system...

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by bbsux, Dec 9, 2008.

  1. bbsux

    bbsux Custodian

    Messages:
    23
    Location:
    Lincoln NE
    I am thinking of setting up a rain water system to be used for toilet water. I'll have the tanks in my basement and have them go thru several filters. I also will have it setup to make up with line water if the tank is too low in the basement.

    Can I use a system similar to a well pressure system? They have a pump and a 2 gallon or greater tank to get it to normal pressure, correct? I would think a 4 gallon tank would be enough for two toilets...

    Thanks
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,154
    Location:
    New England
    Often, a storage bladder tank is described as the total water it could possibly hold. Well, part of that tank will be captive air, so it might only hold a couple of gallons of useful water. A larger tank may be required. To save pump cycles, it might be good to store enough to flush 3-4 times in case there was a rush, say just before going out - everyone uses the toilet.
  3. gardner

    gardner DIY Senior Member

    Messages:
    222
    Location:
    Ontario
    Do you want to use normal off the shelf toilets designed to work from 40+ PSI supplies or would you consider hacking your toilet to fill instead from a low pressure pump controlled by a float switch in the tank?

    How will you hook up your reservoir to fill from line water? You will have to be secure against back-siphon and an air-gap would be required by code, I bet, at the very least. So what sort of valve arrangement would you use to control the fill from line water?

    No idea where you are, but have you looked into whether there are code regulations for this? I think around here the potential for some future owner making interconnects between the rain and city water systems would have the inspector frowning.
  4. Gary Swart

    Gary Swart In the Trades

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    Location:
    Yakima WA
    I think you time, money, and effort could be put to better use.
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,154
    Location:
    New England
    Let's not be too hasty...I've lived in places where the only water was trucked in, so rainwater for acceptable uses is very desireable. Course, those places were in the desert where we got almost no rain, but I can see a use, especially if you already have the storage tanks.

    Yes, you could make up a system as if it was a shallow well. You would have a pump, bladder tank. You'd also want to have a low-limit cutoff in case the tank got too low...running a pump dry will kill it quickly. You aren't particularly interested in long durations of use...a toilet would fill fairly quickly, so a bigger tank filled with a small pump that couldn't keep up isn't an issue - it would save money on the size of the pump and operating costs. If you ever thought you'd have enough water to use it for irrigation, you'd want a bigger pump and bladder tank.
  6. bbsux

    bbsux Custodian

    Messages:
    23
    Location:
    Lincoln NE
    I'd be willing to use a low pressure system but I think it'd be hard to get the water up to the toilet on the second floor.

    The reservoir will be several plastic 50 gallon barrels. I plan on having a electric solenoid controlled by a float with a backflow preventer. So if there isn't enough rain water it will just add from the main water.

    I plan on just running a isolated 1/2" copper line to the toilet and making the whole thing removable -- It won't be staying if I sell the house.

    I thought of using gravity but my attic is uninsulated, and the energy used to pump it up there wouldn't be worth it.
  7. gardner

    gardner DIY Senior Member

    Messages:
    222
    Location:
    Ontario
    I used be in southern Vancouver Island in an area where it rained plenty, but there was limited surface water and nothing but hard rock straight down to the centre of the planet. Until the city brought in water in 1998 or so, everyone had theirs trucked in and this kind of rainwater catchment was pretty popular.

    All this aside, if the OP has city water, I can't see it being cost effective to do this project. A better use of the $ would probably be to put in a super low flush john.
  8. gardner

    gardner DIY Senior Member

    Messages:
    222
    Location:
    Ontario
    ...which doesn't mean I'm not curious.

    How will you plan to regulate the filling of the barrels from rainwater? Will the Barrels be below grade? If so, where does the rainwater overflow go? It is likely forbidden to put excess rainwater runoff down the sanitary sewer. You may find yourself having to pump the excess water back out.

    For the pump, I would recommend a low volume diaphragm type pressure pump like many available from Shurflow. They are popular with the off-grid and cabin/cottage set. I have a 12 volt one that pressurises a 10 Gal pressure tank at my cottage and it works great. A diaphragm pump will operate dry without damage. The one I have will deliver 1.5GPM or so at 40PSI.
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