Anyone have any experience (purchasing or installing) a GFX greywater
Seems like a pretty neat concept but the retrofit details seem a bit
troublesome for an exisitng home.
Their website is a nightmare to understand / navigate.....they appear
to have over 20 different models.
A propane fired water heater makes for rather expensive hot water esp
when the incomming water is ~40F so I have a $ motitvation.
I might (easily) be able to capture the output of two showers but the
third would require a pump.
And in some cases, like here in southeast Texas, retrofit is nearly
impossible!!! Land is ruler flat, and soil is so heavy with clay, we
could make crude pottery with it!!
Retrofit works when you have a basement with NO downstairs plumbing,
Mom's house has a basement, clothes washer installed there.
Good idea, GFX, but not easily adaptable to every situation.
Also, I worry about heat loss in the pipe and asked the GFX tech people
about insulating it. The rely was Nah, don't worry. The only
consideration is that in cooler climates, unlike here, the cold water
entering the coil can cause condensation. In that case, some insulation
is desirable JUST to prevent condensation from building on the coils and
dropping onto the floor.
What do you do with warm greywater now? Do the same with cool greywater?
You might still reclaim heat from an upstairs shower, or add a pump.
Some people say just stick to showers vs sinks and washing machines,
since they are cleaner. If we pump 10 gpm at 100 F with 100 watts
and heat 10 gpm from 55 to 95 F, what's the net energy gain?
I've been working on a different type...
Newsgroups: ... alt.home.repair
Subject: Greywater work in progress
Date: 7 Apr 2006 07:24:57 -0400
Gary Reysa and I are now exploring a greywater heat exchanger with 3 100'
PE pipes (cut from a $60 300' piece) inside a $30 100'x4" corrugated black
plastic drainpipe vertical helix wound around a 2' square x 6' tall bolted
2x4 frame with a 4" horizontal thinwall PVC T at each end:
Warm greywater would enter the upper vertical side arm of the upper T and
cool greywater would leave via the upper vertical side arm of the lower T
and flow up into a vertical 6'x4" pipe and out the top into a septic system.
Cool fresh water would flow from a garden hose in through a cap at the end
of the lower T and up through the 3 1" pipes, and warm fresh water would
flow out from a cap at the end of the upper T into another garden hose and
into the drain tap of a conventional tank water heater.
The PVC Ts would meet the Hancor corrugated pipe with a $16 Fernco 1070-44
fitting. This 4" rubber sleeve has 2 hose clamps and a molded O-ring on
one end which fits into a pipe corrugation. It says "Overtightening of
clamp on this end of the coupling can collapse pipe wall," but it looks
like sliding a $1.28 3" thickwall PVC pipe coupling inside the corrugated
pipe will allow a waterproof 3 psi joint. As a cheaper alternative, this
might also work with a $5 Fernco straight 4" coupler.
So far, the hardest part is dividing the fresh water into 3 pipes with
an inexpensive manifold at each end that will slide into a 4" PVC pipe.
(Ferguson sells 6" Ts and 6"-4" reducers for $19 each!) Here's a Lowes
parts list for an equilateral version that clears a 4" pipe by about 1/4":
Qty Part # cost description
1 PP25052 2.04 3/4" MHT-3/4" FIP brass hose adapter
1 436 007 0.27 3/4" PVC male adapter
2 401 010 0.76 3/4" PVC Ts
2 409 007 1.48 3/4" PVC street elbows
3 437 131 1.41 1"x3/4" PVC bushings
3 436 010 1.32 1" PVC male adapters
3 435 010 4.86 FPT-1" grey PVC barb adapters
1 49303 0.32 2 1"-3/4" reducing galvanized conduit washers
3 105 733 4.29 6 3/4"-1.5" SS hose clamps
$16.75 total, per end
The hose adapter and 3/4" male adapter would screw together through a hole
in a flat 4" PVC endcap, clamping the conduit washers and a rubber washer
to make a low-pressure bulkhead fitting. Trimming the Ts and elbows might
increase the 4" pipe clearance to 3/4". The lower T would have a male hose
thread and inline valve protruding to backflush the greywater path, perhaps
once per year.
This lacks the desirable thermal stratification of a drum heat exchanger
with different greywater inlet temps (altho our tests didn't show much of
that), but it's simpler to build. The 1" pipe holds 12.5 gallons of water,
so this might be close to 97% efficient (saving ~$300/year) with smaller
hot water bursts or a slow greywater flow, as in a chemical-free hot tub
with continuous water exchange. Something like this would also help:
In alt.solar.thermal firstname.lastname@example.org wrote:
I thought I had a four foot vertical drop in my blackwater line, but I
forgot that there's over two feet of slope in the sewage line from one end
of the house to the other.
Given the high energy recovery noted above, I might do well to install a
pump just for the shower, to raise that greywater to a point above the
laundry room, and run that pump only for showers.
I could join the shower water at that point with the washing machine
output, which is not as hot, but is already elevated, and near the water
heater, and make economic sense of this.
The dishwashing machine could be plumbed in as well, since it also has a
high standpipe for anti-siphon purposes, and hot exit water, but that's not
The idea of using the thermal recapture in two or three spots also would
allow use of the smaller, much cheaper GFX units, maybe totaling less cost
than one 4" installation.
Your example, above, is only calculating energy expended during the
recapture of hot waste water, but the original example would have been
pumping all waste in the house, hot and cold, which I don't think makes as
I have always thought that greywater should be plumbed separately anyway,
allowing it to be used as desired for toilets and gardening.
Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8,-122.5
I think in some areas there are plumbing code issues.
But I knew a retired engineer in Michigan that when he built his retirement
home, he had black water and grey water drains separated. Ran the black
water to a conventional septic system, and the greywater to a less involved
After ten years, the septic system installer offered to open up the tank for
the 'ten-year warranty' inspection. When they did, it was remarkably
'clean' in that it did not have much silt or other 'non-degradables' in the
tank. Of course, the septic tank had a pretty low flow rate with just a
retired couple and no greywater.
I too have often thought this is a good idea. Especially when not on city
Greywater/blackwater now get equal treatment, straight up tot he city sewer.
Single story home, so NO opportunity there.
For slab type construction, with heavy clay soils, the easiest install
is to dig a pit down to where the outgoing sewer can be intercepted,
routed to a sewage ejector which pumps to the top of GFX (or your
alternative exchanger). Waste water from heat exchanger then goes to
Seems like separating gray water from black water is impractical, EXCEPT
in two cases.
1. New construction
2. Retro fit in a house with a basement and NO downstairs plumbing,
i.e. you can easily identify and separate toilet drains form sink/shower
And I am coming to the conclusion that I should route the output of the
heat exchanger to both shower cold taps and to the hot water heater.
Water here is warm enough that I do not want to heat sink water, it then
goes from 70sF degree water to high 80sF water.
See below, basements are not possible, swimming pools remain filled year
round as the soil will LITERALLY pop them up out of hte ground, or CRISH
MUST have a pump as the top of the heat exchanger is ABOVE the drain of
EVERY sink, shower, washer,... EVERY water source in the single story
house. No basements POSSIBLE in this soil, the walls would be CRUSHED
under the hydraulic forces of the soil as it alternately aborbs and
Both, lower water heater temp, AND route heat exchanger output to BOTH
Hot water and shower cold side.
Try visiting Houston TX or Dallas/Ft Worth or East Austin TX after a
heavy rain, 2-3 inches over a 24 hour period, maybe two or three such
rain storms over a week.
A single standard shovel of this stuff weighs on the order of 80 pounds!!!
It crushes concrete like it was nothing over a period of 20 years..
Do a web search for GUMBO SOILS
Basements are NOT POSSIBLE, unless a multistory commercial building is
sitting on top of it. A residence is NOT heavy enough to keep the
basement in the ground. The house will gradually FLOAT to the top of
the soil level, busting every water and electrical connection to it.
Either float to top or be CRUSHED by the hydraulic forces of the
expanding and contracting soil.
The ONLY way to make a GFX work is to install pumps to small GFX units
at every shower (even then you will need to piece the slab to gain
access to the drain), OR you pierce the slab ONCE, install a sewage
ejector and run all waste water thru a single heat exchanger. Even them
the piercing of the slab is DANGEROUS to the long term health of the
slab UNLESS you line the pit with sand, stuff it full of welded rebar
tied into the rebar in the slab, leaving a pair of PVC pipes in place
for sewage to run in and out (to city sewer or septic tank) and fill it
with concrete, leaving a void at the center for ejector tank to go.
literally, truthfully, NO OTHER WAY TO MAKE THIS WORK other than the two
scenarios I mention here.
We're getting a little topic drift
I was looking for someone with installation or specification experience
w/ GFX product.
I'm not looking for theoretical discussion, I want some real world
What model did you buy, how did you size it / choose it, how did you
install it, how has it worked out?
The illustrations at the bottom of the page show this insulation
(actually Sch 20 PVC pipe split, the rapped around the coils and
strapped/tiewrapped/taped/glued in place).
As DOE studies show, areas with colder water get better benefit as the
GFX will raise temps of cold water better than warm water.
Optimum case is to route GFX output to shower's cold side, AND to hot
water tank/tankless This is only practical in new construction or a
MAJOR bathroom remodel.
And what can you actualy save or recoup with this. With my tankless ng
WH I pay 5-6$ in summer for all Ng, I have little to recover in
Look into a Takagi TH1 a 94% efficient condensing tankless propane WH.
its Energy Factor is apx 30% greater than any propane tank home WH. Here
you will see measurable savings of propane.
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