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Potable RWH Water (RWH) & Water Testing


The Potable Water distribution system delivers harvested rainwater from the cisterns on demand for:
  • Water treatment and filtration, described below.

  • Potable water distribution within the house for shower, sinks, toilets and clothes washer.

A 3/4" PVC pipe from the cisterns connects to existing house water pipes, separated from the Palo Alto City water supply by a reduced pressure principle flowback preventer. The City water supply supplements the treated RWH water when the RWH water supply is insufficient for domestic needs, e.g. during the dry season. The RWH conduit connects to the house pipes ahead of the City water supply and before the water filtration system.

Potable water is supplied for house use after filtration and water treatment, including water softening.

RWH Treatment and Filtration

The RWH filter system is mounted on the inside garage wall. Its main components are:
  • WH2-HF High Flow 5 Micron carbon block filter package, with:

    • Liquatec's (now Hydronix ) SDC-45-2010 multi-layered 10-micron sediment filter.

    • Pentek's EP-20BB 5-micron carbon filter, which removes organic compounds and reduces odors.

  • The Trojan UVMax Model D4+ UltraViolet filter destroys microbial organisms, and completes the RWH conversion to pure potable water.

  • Pelican Water Systems' NaturSoft NS-3/6 salt-free water softener with sediment filter softens the water for household washing, bathing and drinking.

  • Pentek's RO-2550 Reverse Osmosis system to keep lime scale and hard-water compounds from clogging automatic coffee makers, etc.

  • Trojan UVMax D4+ UV Intensity Monitor and power supply. The monitor's alarm warns of declines in the UV lamp's power and intensity, and of any failure in the power supply. Annually the monitor's LED display warns when the UV lamp needs to be replaced.

    Potable Water Distribution

    Potable water is distributed throughout the house via the existing house piping in the slab, for:
    • Cold-water applications: clothes washer and two Ultra Low-Flow (ULF, 1.3 gallons/flush) toilets. Nowadays newer High-Efficiency Toilets (HEF, 1.3 gallons per flush) are on the market.

    • Hot-water applications: shower, kitchen and bathroom sinks.

    The Stiebel Eltron Tempra 20 Electric Tankless Water Heater ( TWH ) supplies hot water instantaneously on demand to shower baths and sinks, drawing pre-heated hot water from a solar water panel mounted on the roof. The solar panel acts as a 31-gallon hot water storage tank. The electrical TWH also replaces the natural gas water heater.

    The filtered and treated water was tested by a professional testing laboratory according to EPA standards, or higher, to ensure that the water is safe to drink. We intend to retest the water annually.

    Water Testing

    Rain- and groundwater can be contaminated a range of potentially harmful substances, such as bacteria (coliform & E.coli), organic (VOC) and inorganic chemicals, pesticides, etc. It's critically important to test RWH and filtered water periodically to protect anyone who drinks the water from possible harm. Even if treated water were used only for showers or washing clothes, potentially harmful or toxic elements may be ingested. Water testing by a commercial or government laboratory is an important measure for protection.

    Test labs used to date:

    • Performed end-to-end tests for between 166 and 216 contaminants at EPA standards or higher, with approximately 2 weeks turnaround. The company president responded promptly by email to follow-up questions.

    • Tested a sample of water filtered just after final, UV filtration and prior to entering the house, for the presence of coliform bacteria and e.coli. Quick turnaround, but time-sensitive shipping from California to Maine to is very expensive!

    Online research unearthed three main types of water testing laboratories. The Resources & Links column contains a listing of their websites [ Note: Naturally we can NOT endorse any lab whose services we have not used ].

    1. Labs conducting end-to-end testing of the entire spectrum of water contaminants, with testing prices ranging from $150-200 to $500-1,000+, and generating a complete report. The high-end tests are often customized, and geared mainly to commercial or governmental entities serving the public.

    2. Laboratories that test for individual contaminants, e.g. coliform, VOC, selected pesticides, etc. Users submit samples in a bottle, and the results are either positive/negative or numbers, of e.g. bacteria, found. Prices range from $40 to $1,200 per test suite depending on the specific test, but are generally less than $100.

    3. Suppliers of DIY (do-it-yourself) test kits: The customer tests a sample for positive/negative or content. Prices: $8 - $575. If positive, some vendors will analyze the sample, at an additional charge.

    Water ( & Other ) Test Services

    Laboratory / Supplier Consulting Projects Unit Testing Spectrum Testing DIY Test Kits
    Curtis & Tompkins Laboratories, Berkeley, CA - - -, Monrovia, CA - $50 - $200 per test suite $10 - $200
    Envirofocus, Inc., Sacramento, CA - - -
    Envirotek Laboratories, Mullican Hill, NJ - 36 - 240 contaminants
    ETR Environmental Testing & Research Laboratories, Leominster, MA - $40 - $1,200 per test suite -, Bordentown, NJ - 189 to 239 contaminants -
    Northeast Laboratory Services, Waterville, ME - $15 - $80 - -
    Simpltek, Commack, NY - - - $8 - $575
    Torrent Laboratory, Inc., Milpitas, CA - - - (National Testing Laboratories), Ypsilanti, MI - $83 - $103 per test suite -
    Note: Some of these companies offer other test services besides water testing.


    Equipment & Service Vendor & URL
    Water Treatment & Filtering Home Plus Stores, Kamloops, BC, CANADA
    Viqua Trojan Technologies Company, Guelph, Ontario, CANADA
    Pelican Water Systems, Deland, FL
    Waterfilters.NET LLC, Apex, NC
    Water HeatersE-Tankless Water Heaters Corp., Kamloops, BC, CANADA
    Water Testing, Bordentown, NJ
    Northeast Laboratory Services, Waterville ME
  • Resources & Links

    Potable RWH Water

  • Texas Commission on Environmental Quality, Rainwater Harvesting for Indoor Use
  • Water Conservation in Santa Clara County
  • Water Treatment per EPA
  • Wholly H2O - California Integrated Water Reuse Management Center
  • National Sanitation Foundation
  • Puralytics, Inc. Shield 500 LED Filter

    Water Testing Laboratories