PLUMBING
A WATER RETURN MANIFOLD - GOODBYE POWERHEADS!
by ANTHONY CALFO
Sponsored in part by:
One
of the most frustrating aspects of aquarium-keeping with
marines is creating optimal water movement in the display.
Success is often hampered by other common flaws in planning
and plumbing, like inadequate drainage (hole numbers and
sizes) and the very rockscape of the display, which too
often is crippled without a 4” minimum distance from any
wall. Water flow issues can literally make or break a
tank. Some popular fishes express neurotic behaviors like
“pacing” in slow-flow environments: swimming back and
forth against the glass relentlessly as if pursuing their
own reflection. Some tangs, for example, will cease this
behavior with increased water flow. Sessile reef invertebrates
depend on accurately applied water flow to bring food
to them and to carry waste away. Their very lives will
be threatened furthermore in poor flow environments over
time and in ways that some aquarists can easily overlook,
like encroachment by algae and poor gas exchange from
the increased thickness of the microlayer than runs anoxic
near their body. The dynamic snowballs as waste accumulates,
mucus accumulates, bacteria proliferate and ultimately
become pathogenic; it’s the very thing that kills so many
corals in shipping. There is also the simple matter that
an increase of water flow in traditionally under-filtered
aquariums often translates into prompt and improved rates
of growth in captive animals. And finally, on more elemental
level, effective water flow is necessary in the aquarium
to prevent the accumulation of detritus, and worse - lingering
matter that dissolves and concentrates over time (i.e.,
- 20% water changes still leave 80% of the undesirable
contaminants generated behind to accumulate). Good water
flow will keep solids in suspension, which increases feeding
opportunities by fishes and invertebrates, and improves
filter/skimmer opportunities to export such matter in
a well-designed system.
Powerheads
are certainly one of the most popular ways aquarists create
water flow in the aquarium, yet the technology has its
flaws and may not be appropriate for advanced marine systems.
They are generally constructed for short to medium-term
life, with many being so inexpensively constructed and
offered that they are regarded as “disposable”. Some will
last more than five years (uncommon), but even they are
generally “tired” and only able to provide reduced flow.
Most have a useful lifespan of less than 5 years. While
we are on the topic of failure and modest construct –
what about shock hazards? Good heavens, it is amazing
and frightfully common how many people have gotten a shock
from a faulty powerhead! Yet it is not actually surprising.
Take a look and you will find that most have non-grounded
and even non-polarized plug ends that are simply epoxy-sealed
into the motor housing. That seal has a limited life…
and so will you if you neglect to employ a proper GFI
(ground fault interrupter) for your wet aquarium station.
What else can we fault powerheads for? Imparted heat –
a silent problem inherent with any submersible pump and
amplified here by the number of units sunk in the tank
to achieve the same water flow as a single cool-running
external water pump. For displays with other heat issues
(like enclosed and poorly vented lighting systems), powerheads
used for primary water circulation contribute more than
a few degrees to the water temperature, which can be a
serious problem. Of lesser concern but still worthy of
mention is the risk that their unguarded intakes pose
to aquatic life. Many aquarists have lost animals unnecessarily
this way - particularly benthic motile invertebrates,
slow/weak fishes, and anemones & toxic sea cucumbers
that wait until you go on vacation to drift. Guarding
the intakes instead increases the need for upkeep unduly:
a small guard clogs quickly, and a large guard runs the
risk of becoming an unwelcome nitrifying surface. In systems
with high flow needs overall, it may take 4 or 6 or more
powerheads to produce the same flow as a single external
pump. And at last, power heads are staggeringly unattractive
and distracting in the display proper to many observers.
Their only saving grace is that they are cheap and affordable,
which allows newer aquarists in particular to “buy into”
the hobby – a very important and worthwhile distinction.
This article,
however, is not likely to be directed at new aquarists.
While the application of a water return manifold is simple
enough to construct (and mere dollars worth of plastic
for most), concepts of sumps and hard plumbing with valves
and adjustable fittings are unfamiliar if not daunting
to the truly novice participant. Old, salty dogfish however
(experienced aquarists, that is…), have earned honorary
degrees in chemistry, carpentry, plumbing and electrical
engineering to become reef aquarists. Hopefully, some
well-prepared and researching new folks will read this
and be spared the gauntlet of powerhead pits just the
same. Advanced aquarists are charged to pass the word
along in kind if they agree.
Depicted
here, the rudimentary skeleton of a simple water return
manifold. The primary purpose is to offer greater control
over the finesse of water flow in the display. Its teed
outlets get fitted with fine adjustable aspects – see
text below. With this application placed at or slightly
above the water surface, one can avoid unsightly powerheads
in the display while also reducing their expense and
redundancy, beyond issues of poor flow control and excess
heat imparted by them. Illustration by Kevin Carroll
Harnessing an external water pump, a manifold of PVC is
to be plumbed with a single feed line. [Please refer to
the 3-D manifold illustration atop this article for a
visual cue to the continued description of its general
employ – sump version shown] This feed pipe runs up to
the manifold and taps in by a tee. Branching off below
this closed loop for any other applications is not recommended;
we need a dedicated supply of water here. Obey the manufacturers
recommendations for line size. Home aquariums of a couple
hundred gallons or less will likely use 1” or ¾”
pipe. Larger pumps and systems will use accordingly larger
plumbing for this purpose.
The manifold
ring/loop of PVC is closed in a complete circuit to help
balance the water dispensed from each outlet. Control
nozzles will afford the final tuning needed in this regard.
Most folks build their manifold the size of the inside
perimeter of the display tank. For aquariums with a commercial
plastic trim, small holes can be drilled in the recessed
lip for plastic ties (cable/zip) to be fished through
for securing the suspended manifold. Bare glass aquariums
(no trim) can have fasteners (plastic hooks, cable ties,
etc) embedded into a dab of silicone near the edge and
put to use once the caulk is cured. Acrylic aquariums
are very accommodating and can easily be drilled or glued
with whatever fasteners work best and are most discreet.
Placement of the manifold at or slightly below the water
surface (the nozzles at least) reduces or eliminates any
issues with salt creep or salt spray.
Tapped
into the manifold ring we need multiple tees,
angled slightly downward as a good-sense precaution
in case the nozzles leak or become “liberated”.
The placement of these tees is not of much
critical concern as long as you have enough
in total to work with; the ability to manipulate
water flow through any of them is very flexible
and efficient. I’ll suggest 4 to 6 teed outlets
per 100 gallons of tank volume, spaced evenly
apart, as a starting point. Frankly, you should
have no fear constructing a manifold for how
inexpensive the framework is to build. In
the worst-case scenario, a scrapped structure
is a lesson of $20 or less in plumbing, which
is a pale and worthwhile investment in light
of the value of the display tank.
Next
we must decide on the type of nozzle for inside
of the manifold tees. They should be movable/swivel…
and ideally be able to restrict or regulate
water flow. It’s at this point where the project
can get as expensive and complicated, or not,
as you like. To keep expenses very low, PVC
elbows (usually 45-degree) and nipples (short
lengths of pipe) are the best way to go. Fittings
for small plastic pipe generally cost well
under $1 each, or several for a dollar in
bulk. A single stock length of straight pipe
is like-wise but a few dollars. Short nipples
of pipe (1-3”) can be used to connect unglued
45-degree elbows to each teed outlet. The
tapered slip sockets of the elbows will afford
a snug and water tight seat without committing
to a glued position. They can then be swiveled
to finesse the dynamic of water flow in the
aquarium as corals grow or wane, or when the
seascape changes for any other reason. A slight
restriction of water flow can be achieved
by heating another short stem of pipe and
crimping it to produce a restricted flare-tip
that will increase the velocity of effluent
water. This modified nipple is to be placed,
of course, into an effluent tee. Some discretion
is required here, however, as the resistance
from a single crimped outlet will likely translate
into water taking an easier path of resistance
– namely, another open outlet(s). To compensate
for this, all outlets need to have similar
modifications/restrictions, or valves will
need to be installed for each outlet. Valves
are not emphasized here as they add considerably
to expense, are generally not needed, and
complicate a delightfully simple application
to excess (creating a “juggling act” with
one adjustment affecting all). Another concern
is that if the manifold does not have enough
outlets, there will be undue pressure placed
on the pump (generally harmless for magnetic
drives, but perhaps harmful to direct drives).
On the opposite end of the spectrum, if too
many outlets are installed (more is generally
better/safer for future pump upgrades), they
can easily be capped (glued or unglued) with
a PVC cap and short stem/nipple. Truth be
told, most tanks will be served very well
with unrestricted outlets that merely have
swiveling 45-degree elbows.
Proud
sponsor of this column
Nonetheless,
some aquarists will have more discriminating
preferences… and some corals certainly have
more demanding needs regarding water flow.
This is especially true in display with large
or fast growing corals that have a monthly
need for modifications in the delivery of
water flow. While the above-mentioned swiveling
elbows have a very wide range of motion and
coverage, there is an even better option:
flexible ball-socket joint tubing (wide industrial
usage, but found in the aquarium trade at
comprehensive LFS shops and online at www.marinedepot.com,
and elsewhere). This interlocking pipe is
much more expensive per foot than standard
DIY PVC parts, but very little of it is actually
needed. The product line is complete with
numerous adapters for connection to PVC plumbing,
as well as add-on fittings to manipulate the
ou-going water. A short length (perhaps just
3-6”) is all that is needed on the end of
each teed outlet on the manifold to superbly
finesse water flow in the aquarium as needed.
Clearly, effluent direction on the manifold
can be tweaked and tuned in ways that are
impossible with rigid and planar powerheads.
Ultimately,
the goal with any interpretation of outlets/nozzles
that you may choose to employ is to get the
outflow paths to converge in the water column
to produce random turbulent circulation that
is nearly as ideal as surge motion but far
less complicated to produce. Dump and surge
buckets/devices produce excellent water movement
but are generally noisy and inconvenient to
install and operate. They are often finicky,
and produce problematic snapping and micro-bubbles,
and excessive salt creep that is unduly warranted
for a home aquarium. They are also cumbersome
in size and aesthetically detractive for most
living spaces. Such devices are better suited
for very large systems, like public displays.
Wave-timers with powerheads are likewise inferior
to dedicated pumps producing random turbulent
flow as their staccato operation increases
wear on pumps in use while robbing the system
of potential water flow during “off” cycles.
Truly, the closed loop manifold described
herein produces some of the most efficient
water movement in the aquarium while insuring
a good value of use (pump life and “bang for
your buck” regarding watts used to produce
X measure of water movement).
Profile
of a small reef (36” long - 50 gallon)
with a partial manifold (loop is not
closed and nozzles not installed yet).
Notice the discreet feed through a
back wall bulkhead (upper left side
of picture), covered by a black shield,
fed under the central brace and secured
to the obscuring upper front trim
of the aquarium with plastic cable
ties. Note: the PVC fittings siliconed
to rear vertical glass panes are deliberate
pockets for corals to encrust upon
behind the rockscape for dimension
as the tank matures”. photo by
Anthony Calfo
Aquarists
for some time have also used external water
pumps plumbed directly in and out of an aquarium
(no open sump necessary) in a fashion that
is called “closed loop”. It lacks a manifold…
and actually, lacks any notable means of finesse
– it’s simply an external water pump sucking
water out of a tank and blasting it right
back in. It is crude, but serves a very important
role in aquariums with high flow demands that
exceed the desired (or able) abilities of
a sump path return often hampered by inadequate
overflows. [Please don’t get me started on
a discussion of the ill-conceived and so-called
“reef-ready” aquariums being sold commercially.
I still cannot fathom what kind of reef they
envisioned with their meager holes/flow rates.
Their flow-through capacity is crippling…
hello algae!] A closed loop pump on the display,
with or without a sump installation, can be
harnessed to power a manifold as described
above. Since the intake is tapped through
the display body wall, and the return is at
or above the water surface, there is no risk
of an overflow as with a sump from return
lines that dip too low and back-siphon in
the event of an interruption of power (assuming
the safe running sump level was not calculated
and obeyed). There is some concern, however,
with the protection of the pump intake: it
is more dangerous than small powerhead intakes.
The literal placement of such pumps is also
somewhat to very inconvenient for servicing.
It is for these last reasons that I personally
prefer to run a manifold off a proper sump
pump
With
any external pump installation, please be
absolutely sure to use flanking slip unions
(quick disconnects) and shut-off valves -
see illustration. This will allow fast and
tidy removal of pumps for cleaning, servicing
or replacement. Neglect to heed this aspect
of proper installation has often resulted
in many hours of hard labor and frustration
by aquarists that have hard-plumbed pumps
inline and then were faced with draining a
tank to remove them.
By
category, external direct drive pumps are
admittedly not quite as energy efficient as
internal magnetic drive pumps (powerheads).
But, as previously stated, they are more durable
(regarding wear/abuse and lifespan), and they
are more powerful (operating against greater
pressure/resistance/head). Yet, some modern
external drive pumps are remarkably efficient
and competitive. They may use less total energy
overall than the number of powerheads required
to produce the same flow. At the very least,
they will save money on spared replacement
costs over time (replacement of powerheads)
and are safe for the aquarist and its tanks
inhabitants at large.
In
this article, I hope to have succeeded in
bringing to light an inexpensive, discreet
and effective DIY strategy for manipulating
water flow in the aquarium. If you find utilitarian
merit in it, pass it along to a friend and
let’s watch such techniques evolve in time.
