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5. Plumbing and Pumps

A typical setup

Use vinyl tubing and barb fittings for the return lines.
All things considered, you get the most overall flexibility, utility, and ease-of-setup. Our opinion and based on our observations. Those that “swear” by hard plumbed PVC and/or flex PVC seem to like Rube Goldberg contraptions and consider it a sign of a professional install.

What is the difference between PVC, CPVC and ABS?
These are three different types of plastic pipe used in plumbing applications that are joined by solvent cementing: PVC (Polyvinyl Chloride); CPVC (Chlorinated Polyvinyl Chloride); and ABS (Acrylonitrile-Butadiene- Styrene). PVC and ABS pipe are normally used for Drain, Waste and Vent (DWV) systems, while CPVC is used for water distribution systems. PVC pipe can be used in pressure applications – such as water mains, service lines and irrigation. It is important to choose the correct solvent cement based on the type of plastic pipe being used.

For threaded connections, always:
Use Teflon® tape or approved paste thread sealant. Assemble threaded joints carefully (maximum two turns past finger tight).

For the drain(s),
again consider vinyl tubing or plain old corrugated drain hose.  For redundancy, employ multiple drain lines should one get blocked somehow at or after theoverflow.

Never reduce the intake of any pump.
This will shorten the life of the pump and will cause it to run warmer than normal.

Try not to reduce the return of the pump either.
The return line coming from the pump should only be reduced at the last possible moment in order to decrease resistance from friction and help the pump run cooler. While reducing the return line at the pump will increase shut-off head somewhat (like putting your thumb over a garden hose to make it squirt farther), it will also increase resistance against the pump’s impellor, shortening the life of the pump and making the pump operate at a higher temperature.

Always use a screen on the intake side of the pump.
The screen should be designed for this purpose. Most submersible pumps come with a detachable screen. If you are drawing water from over the side of the tank or reservoir using a hard plastic J-tube, make sure it is equipped with a screen. If you are using a bulkhead fitting to draw water through a panel of the tank or reservoir, then obtain a screen designed to fit into the tank-side of the bulkhead. Most bulkhead kits come with a screen.

If possible, you should use a plumbing line to feed the pump that is larger than the pump intake diameter, reducing the diameter right at the pump. This will ensure that the pump runs normally by flooding the intake, even if the intake screen or feed line becomes slightly clogged by debris.

AVOID HARD PLUMBING IN THE PUMP RETURN LINE!
We cannot stress this enough! Although (to an amateur) a filtration system plumbed with hard PVC may LOOK neater and more professional than one plumbed with flexible vinyl or (preferably) flexible PVC, hard PVC elbows and pipe provide more resistance than flexible tubing. This increases head pressure and makes the pump work considerably harder and operate at a hotter temperature. If you must use hard plumbing (like we do when a client insists in spite of our recommendations), use “sweep” elbows instead of tight 90 degree elbows and be prepared to purchase an aquarium chiller.

If you have to valve a pump down more than 1/3 of the way, your pump is too large for the application. Valving a pump down too much will result in resistance, a hotter pump, and subsequently warmer temperatures in the aquarium. A pump that is too powerful for a given application may “cavitate” (Simply Put – pull air out of water) in the impellor area causing severe damage to the pump.

Don’t use maximum flow-rate handling of a filter device as a guide for purchasing a pump! End-users complain that the pre-filter cannot keep up with the pump. The pump is rated to deliver a certain flow and the pre-filter is rated to handle a certain flow-rate. These are maximum recommended flow-rates. That means that the pre-filter can handle that flow rate UNDER IDEAL, PERFECT CONDITIONS! These hobbyists have taken the maximum flow the pre-filter can handle, and matched their pump to deliver the maximum flow. That can lead to problems because not all variables can be accounted for, such as bends in the pre-filter drain-hose that cause a back-up and do not allow unimpaired drainage.

The maximum turn-over through any OPEN filter system (such as a wet-dry filter) should be no more than five times the volume of the aquarium. The maximum flow of a closed system (such as a canister filter or chiller) can be whatever the system is rated for. Need more current? Add a power head to the main aquarium tank for additional circulation.

When designing a central filtration system that services more than one tank, be sure to balance the system. It is OK to use a single reservoir and pump to deliver water to two aquariums as long as the water returning from both aquariums returns to the same reservoir. It is not OK to use a single canister filter or other closed filter system on two separate aquariums. As water passes along the path of least resistance, one tank will eventually overflow.

Use a separate pump to drive a protein skimmer. Protein skimmers supply varying resistance to the pump due to “scum” build-up inside the skimmer body and valves, as well as partially-clogged venturis and collection chamber vents. If the same pump returning water to your tank from a reservoir is also driving your skimmer, you will find yourself constantly adjusting valves to adjust your skimmer collection rate.

Water pumped from an open system can pass through a closed system, but water draining by gravity from an open system should never pass through a closed system. For example, you can draw water from an open reservoir, pass it through a micron cartridge filter, and have it return water to your aquarium. If, however, you try to pass water draining via gravity from the main tank into a sealed micron filter on its way back to the reservoir, your main tank may eventually flood as the micron cartridge clogs.

For reef aquariums, water current patterns should vary to prevent settling of detritus which can smother sensitive corals and algae. To accomplish this, a “wave maker” device may be used which turns several pumps on and off at different intervals. There are other devices that can vary the water flow in a tank, including rotating return nozzles that operate using the water pressure that passes through them, much like a lawn sprinkler system.

To quiet an overflow, use a gate valve after the drain to adjust the drain rate to your flow rate.  This can create a “perfect” siphon and should run almost silently.