A Domestic RO Water System
What’s in that glass of water?
Although the Undoctored and Wheat Belly program caution about gut flora antagonists,
including treated municipal water, the programs don’t presently endorse any
specific drinking water product solutions. The present article considers choice
considerations, and what one
Inner Circle member elected to do about it. This is not specifically an
endorsement of the filter system chosen.
At right: a sink-mounted drinking water faucet. This particular one
is provisioned by a reverse osmosis (RO) system cable of delivering
about one gallon per minute (2 fl.oz./sec) for a couple of minutes
before it needs to catch up (which takes hours). In typical daily use,
we actually never see the flow rate slack.
Table of Contents
Drinking water in most U.S. homes is alarming. If it kills your house
plants, or you can’t make fermented foods with it, or it has a chlorinated
odor, it’s not fit for human consumption, just due to microbiome effects,
if not thyroid effects.
If it’s from a public water supply, residual treatment chemicals
(many highly persistent chlorides, such as chloramine) are quite likely,
with some likelihood of additional fluoride compounds you might not desire,
if not adverse minerals leeched out of incautiously chosen legacy pipes
(e.g. asbestos). The antiseptic amendments are not a conspiracy.
The goal of having public water
supplies be potable imposes a requirement to not just sterilize the source
water, but to also control pathogens from plant to faucet. That has
unintended consequences in most current implementations.
Even if you are on well water, excess regional minerals and
residual farming or industrial chemicals could be still a concern.[ Return to TOC ]
The alternatives include, broadly:
• retail bottled water
• commercial water delivery
• home water distilling
• counter-top filters
• under-counter filters
• whole-house systems
Before exploring solutions, you need to scope the problem
(what needs to come out of the water), and the logistical goals
(system capacity, cost per gallon, workload, space available,
regulatory constraints, etc.)
Having your water tested might be worthwhile, to avoid under-filtering
or over-filtering. Don’t over-test, either.
If on public water get the most recent water
quality report from the system operator. There’s no point
testing for what they already admit is in there.
Or just fix it. We’ve had ours tested for hardness, and it’s
very hard water, basically liquid limestone, and lots of sediment.
We’ve never had it tested for agricultural residues, but suspect
them, so never used it for drinking. We have a whole-house filter for
most of the sediment, and a water softener for utility use,
but didn’t want to drink or cook with the softened water.
solutions are a nuisance, speaking as a household that lately
ended two different forms of that (one outside the scope of this article).
You have to hump ’em home from the store, store them full, store them empty,
and dispose of them. They are also almost always made of plastic, sometimes
the relatively harmless
HDPE /2\ or
LDPE /4\, but too often
PETE /1\, and
easily some plastic that out-gasses concerning compounds, claims
of BPA-free to the contrary notwithstanding. If refillable, who is
washing them, and with what?
delivery reduces the stewardship hassle a bit, won’t change
the economics much, requires dedicated floor space, but places
some focus on a point above. The bottles are re-used (often
literally until they start leaking at customer premises).
How are the bottles being washed and/or sanitized?
In my last job outside the home, the employer had water coolers
with national-brand-name delivered jugs. About annually,
there would be a distinct detergent flavor to the water.
What does your microbiome think of that?
For the same price, you can probably beat that service.
been there, done that. Noisy, power-hungry, heat-producing,
humidity-generating. Then you might spend more kilowatts to refrigerate and cool the
condensed water, which is still pretty hot as freshly made.
The more junk you need to get out of the water, the more clean-up is needed with a still.
With hard water, you need an ample vinegar budget
for frequent, annoying demineralizations. When I ran the numbers on power alone,
it was just as cheap to buy bottled water, and a lot less trouble.
range from simple Brita-style activated
charcoal filter pitchers to what are really
under-counter systems in a big counter-top box (the size of a microwave oven,
if not larger). We have a Brita, but it’s a backup, and we aren’t super confident
that it does all that much for the calcium carbonate, esp. over the rated life of
If the system is really just an RO in a box, it’s going to have
a brine tank that must be emptied regularly, or need a connection to
your DWV system, or at least be
able to run some inelegant tubing to a sink.
Our counter top space is also entirely spoken for, so more elaborate c-top devices
simply didn’t make the cut (entirely apart from brine complications).
are available in a challenging variety and a wide range of prices.
In our case, as with the counter-top, we didn’t want to surrender
the under-counter space (plus, routine system stewardship is an
awkward affair under-counter).
what we did instead was to get an under-counter system, but
install it remotely, shown at right (system tour at end of article). The product
depicted here is a Pure Water Products ro003
Whole house systems
may filter the water for all domestic uses, possibly including
some that don’t really need it, like washing the car or the
laundry. On the other hand, do you really want to water the
garden or lawn with municipal halogen compounds that kill house plants?
A real benefit could be in bathing. If our house had been on
muni water treated with chloramine, I would not want to shower
with it. Skin, eye, ear and orifice microbiomes —
yes, they’re a thing, and even less understood than gut flora.
Point-of-use showerhead filters are available. If they’re intended for chlorine
removal, make sure the claims specifically include chloramine.
Major considerations for whole house are the capital and consumable expenses,
and the need for a high peak capacity, which might require a
holding tank as large as your hot water heater.[ Return to TOC ]
What type of filtration system to select depends on the problem to be solved.
System types broadly include:
• simple sieving filters (fine screens, dense media)
• ionic methods (e.g. activated charcoal)
• osmotic (e.g. RO)
• chemical methods (e.g. catalytic, reactive media)
• biological methods (algae)
• phase-change methods (e.g. distillation)
or some combination thereof.
If your only concern is for example, chloramine, you can get filters
that remove just that. The demand for such filters is interesting.
I seriously doubt that it’s being driven by microbiome
enthusiasts. I suspect it’s largely epicurean (people
don’t like drinking treated muni water just due to taste)
and to a lesser extent fluoridation fret (where those
people also want to remove the chlorine compounds).[ Return to TOC ]
• regulatory issues
• system capacity
• system price
• consumable sourcing and prices
• system stewardship
• installation expense
• operational validation
There are two main legal
considerations, which may not apply to you at all.
1. Plumbing work
If you live in a guild-afflicted or nanny state,
you may be obliged to hire a licensed plumber for
even the most trivial work.
A permit may be required.
In any event, any tapping
into supply and waste water systems requires someone who has
basic competence in these matters.
Reverse osmosis systems discharge at least 1×
waste water for each gallon filtered, but more typically
As with water softeners, there may be local
legal constraints on installation and use of such
systems. In any event, the drinking water contribution
to any water bill is going to rise a tad. At our residence,
the waste water all goes back into the ground we got it
from, and we get to drink it again in 20 years or so.[ Return to TOC ]
is usually limited by the slowest element of the filter systems,
which would be the RO membrane in an RO system.
In the U.S., systems are usually rated in gpd (gallons per day),
and typically start at about 20 gpd.
Without a holding tank, the live output of a typical
under-counter RO system is quite literally a trickle.
20 gpd is only 1.8 fl.oz. per minute.
Filling an 8 oz. glass would be frustratingly slow.
Holding tanks have a bladder at the center seam, and are lightly
pre-pressurized so that when the filtered water fills them, the
bladder compresses the air until it rises to near
water supply pressure, at about 60% full.
So a "4 gallon" tank has a useful capacity of about 2½ gallons.
For simple consumption, choosing a tank that holds one
gallon per resident is probably a safe target. Don’t forget the pets
and the house plants.[ Return to TOC ]
Anything more elaborate than a turn-key connection-less
counter-top solution needs to include consideration of
$ the kit as advertised,
$ things that really aren’t optional,
$ possibly a suitable structure to mount it on,
$ additional fiddly bits to hook it into house systems,
$ installation expense,
$ sink modifications in many cases,
$ initial consumables if not included, and
$ instrumentation for on-going checking of water quality.
The advertised system or kit price may not be the
total initial capital expense. Does it include a faucet?
Check also for options that would
be wise to have (in particular some way to assess system status).
Make sure the initial consumables are included.
For a system of any complexity or distance, expect to need a few more fittings,
and some extra tubing.
We elected to get the RO system bundle with a permeate pump,
as it nearly eliminates the system pressure drop at the tank, allowing
full rated gpd.
Under-counter systems usually include sufficient runs of tubing,
and fittings (often blind/vampire) for tapping into common
supply and drain lines. In our case, we needed an extra 50 ft.
of tubing, plus a 1-in. tee, shut-off valve and reducing fitting.
The installation was near a basement sump pump, conveniently.
Regardless of system rate and tank size, instantaneous rate
is going to be limited by pressure and pipe size. Typical
under-counter systems use ¼-inch
OD polyethylene tubing,
which is 0.170-inch ID.
At typical household water pressures, expect about 1 gpm.[ Return to TOC ]
matter. A cheap system can easily be more expensive in the
long run if you need to replace elements in 5 stages multiple
times a year (and two of those stages you didn’t need anyway),
and the elements are only available from Bespoke Water Systems,
at high prices, except that they went out of business shortly
after you got the system.
Find out what element sizes are used, who sells them, and for how much.
Do you need to stock a replacement set? Probably not. If you are
replacing based on some measured marker (like TDS),
the measuring device provides ample warning. If on a calendar basis,
just set a calendar event on your mobile device.[ Return to TOC ]
Make sure you know what the expected replacement cycle is,
and with how much hassle at the system. Clearly the system needs
shut-offs at various points in the flow. Ours are at supply, tank,
and system outlet (plus the faucet). Can the system be drained
to minimize spillage when pulling cartridges?[ Return to TOC ]
If you have to hire a plumber, get a quote.
If sink, counter-top, floor, wall or structure penetrations are
required, make sure that’s accounted for.
For an actual under-counter install, get the dimensions of the
system, and find out what support it needs. Include clearance
for filter removals. In our case, a frame
was easily constructed from lumber scraps left over from other
projects. A couple of brackets were bought to support the
At point-of-use, a porcelain sink that lacks a spare escutcheon
opening, or a marble counter beneath,
is going to require special tools, and perhaps a tradesperson
other than a generic plumber. In our case, the counter-top was already
open below the stainless steel sink, but the escutcheon hole was not there.
I coincidentally had a ¾-in. sheet metal punch,
otherwise a tool purchase would have been required.[ Return to TOC ]
Follow vendor instructions for break-in.
Have a plan for checking system performance. Our system came with a TDS
(Total Dissolved Solids) meter (not shown), that checks water conductivity.
In a properly working system, TDS should measure pretty close to
bottled distilled water, which leads to the next consideration…[ Return to TOC ]
Whether charcoal filtered, RO filtered or flat out distilled,
you now have what is essentially content-free water, which is
very far from ancestral stream water loaded
with minerals (and, to be sure, some pathogens). The WB/Undoctored
recommendations for magnesium supplementation are due in large
part to this modern filtered water depletion problem.
Consider adding some trace minerals to at least some servings of that
water. Our household routine is that the daily serving of Mg-water
(made with RO water)
gets ancient mined salt added to it. We’re presently using coarse Redmond
Real Salt in a mill. 3-4 cranks into 16 fluid ounces of water.
This restores some of the trace, but makes no real contribution
to Mg and iodine in particular.[ Return to TOC ]
Your system probably won’t look exactly like this,
but a tour might give you some things to ponder.
Note that no electrical connections are shown. While not exactly fluidic logic,
most RO systems are water-operated, running
on the pressure differential from between the supply and point of use.
In this case, the brine outlet of the RO membrane (3) operates the
permeate pump (4), which then moves the mostly-filtered water to the tank (5).
- Not shown: 1-inch PVC tee spliced into water supply, after
supply expansion tank and whole-house sediment filter,
but before water softener.
- Supply shut-off valve and reducing fittings: to connect
to the ¼-in polyethylene tubing use (which in this
case relies on John Guest-type push fittings: no compression
fittings, no threaded or solvent fittings, and no soldering).
- Pre-filter: this is a carbon filter, and might be a bit
superfluous, as we already have a sediment filter, but I see
it as enhancing the lifetime of the RO membrane and post-filter.
- Reverse osmosis (RO) membrane: this has three connections, an
inlet, a filtered water outlet, and a brine (waste) water
- Permeate pump: the brine flow (left side) is the motor side.
The right (pump) side is the permeate (filtered water) flow.
This isolates the RO membrane from the back-pressure of the tank,
and also enforces the brine/permeate ratio. Permeate flow here is
probably ¼ of brine flow, as this is a 4:1 system.
This particular permeate pump clicks, which lets you know it’s
working, but might be annoying in some installations. Silent
pumps are available.
- Holding tank: this is a nominal 4 gallon tank, with a useful
capacity of 2½ gallons. We could continuously dispense perhaps 2 gallons before we’d notice the flow diminishing.
The tank fitting has a shut-off valve so that the tank doesn’t
have to be discharged during system servicing (but it might as well
be anyway, because these bladder tanks need to be re-pressurized
periodically — a bicycle tire pump suffices).
this is another carbon filter. I frankly
haven’t studied the cartridges to see how they differ.
- Output line and shutoff valve: this feeds about 50 feet of
tubing to the dedicated faucet at the kitchen sink.
- Brine line: this dumps directly into our main sump pump.
The drop line has a check valve (and there are other check
valves in the system).
installation for our system was expedient. A ¼-in. drill
sufficed for all penetrations (although an extended length bit was
needed through the cabinet floor and sub-floor). The run was tie-wrapped
to the existing cold water plumbing for most of the route, and secured
by cable clamps elsewhere.[ Return to TOC ]
Bob Niland [disclosures]