Do you actually need a pump?

Not every greywater system needs a pump, and adding one when you don't need it means paying for hardware, electricity, and maintenance that serves no real purpose. Gravity-fed systems work when four conditions are all true at your site:

• The unit is positioned higher than your irrigation field
• You have at least 6 feet of vertical drop between the unit's outlet and the nearest emitter
• Your total irrigation demand stays under 200 GPH
• Every section of mainline runs downhill — no uphill segments anywhere

When those conditions are met, gravity does the work reliably. The Aqua2use Gravity unit is designed exactly for this scenario — same filtration, same overflow protection, same installation process as the pumped models, just without the pump.

You'll need a pump if any of the following apply:

• Your lot is flat or the irrigation field is uphill from the unit
• You can't get 6 feet of elevation between the unit and the field
• Your household produces more than 200 GPH of greywater during peak times
• You want to use pressure-compensating emitters, which need at least 7 PSI to operate
• You need water to reach areas that aren't naturally downhill from the unit

If one or more of those applies to you, a pumped system is the right call. The rest of this guide covers how to choose the right one.

How pumps work — GPM, head, and PSI explained

Two numbers tell you almost everything about a pump's capability. Learn to read them and pump selection becomes straightforward.

Flow rate (GPM)

Flow rate is how much water the pump can move per minute — gallons per minute, or GPM. More plants, longer pipe runs, and bigger systems need more GPM. A 10-plant drip system running adjustable valves at 40 GPH each needs about 6.7 GPM. A 30-plant system at the same rate needs 20 GPM. The pump has to deliver at least as much as your system demands, with some headroom.

Head pressure (feet or PSI)

Head pressure is the pump's ability to push water against resistance — uphill elevation, pipe friction, and the minimum pressure your emitters need to open. It's often expressed in feet of head, where 1 PSI equals 2.31 feet. A pump with 23 feet of maximum head can generate about 10 PSI. A pump with 46 feet of max head can reach about 20 PSI.

The critical catch: flow and head trade off against each other

This is the part that trips most people up. A pump that can push 34 GPM on a completely flat surface might only deliver 18 GPM when working against 15 feet of head — and nothing at all past its maximum head. You never get both maximum flow and maximum pressure simultaneously. As the system demands more pressure (taller elevation, longer pipe runs, higher emitter requirements), the flow the pump can deliver drops.

This relationship is captured by the pump curve, which is the only tool you need to understand to make a confident pump selection.

Reading a pump curve

A pump curve is a graph with flow (GPM) on the horizontal axis and head (feet or PSI) on the vertical axis. It shows exactly how much flow the pump delivers at every level of resistance. The curve always slopes downward from left to right — more pressure means less flow.

Matala GR-32 pump performance — the curve that tells you exactly how much flow you get at any given head.

Three points on the curve matter for design:

• Maximum flow (0 ft head): The most water the pump moves when working against nothing. Not useful for real design — no system has zero resistance.
• Rated operating point: Where the pump performs under typical conditions. This is the number that actually matters for sizing. Pump spec sheets usually express it as GPM at a specific head, like "17.2 GPM at 16.4 ft (5m)."
• Maximum head (0 GPM): The highest pressure the pump can generate when water stops flowing entirely. Also not a real operating point, but useful as an upper limit.

Take the Aqua2use GWDD's GR-32 pump as a concrete example. Here's what the curve looks like in table form:

Notice how sharply the flow drops as head increases — from 33 GPM at 5 ft to just 8 GPM at 20 ft. This is why you can't just look at the maximum flow number when choosing a pump. The question is always: how much flow does this pump deliver at the head my system actually requires?

Which brings us to how you calculate the head your system requires.

Total Dynamic Head — the real design number

Total Dynamic Head (TDH) is the total resistance the pump has to overcome to deliver water through your system. It combines three things:

• Elevation head: Every foot of uphill travel between the pump outlet and the irrigation field costs 1 foot of head. Downhill gives it back.
• Friction head: Every foot of pipe, every fitting, every filter, and every change in direction resists flow. The narrower the pipe and the higher the flow, the more friction eats into your available pressure.
• Emitter pressure: If you're using pressure-compensating emitters like Bioline PC dripperline, they need a minimum pressure at their inlet to work — typically 7 PSI (16.2 ft). The WWG kit's adjustable barbed valves are different — they flow at any positive pressure, so there's no minimum threshold to budget for.

Add those together and you get TDH. That's the head value you look up on the pump curve to find out how many GPM you actually have to work with.

Worked example — WWG kit with adjustable barbed valves

Let's say you have a GWDD serving 25 plants across two zones with the WWG drip kit. The site rises 8 feet from the unit to the field, with 75 feet of ¾-inch poly supply pipe between them.

The fix is supply pipe sizing. Step up from ¾" to 1" poly (ID = 1.049") and friction at 12 GPM drops from 8.5 to 2.8 PSI per 100 ft. Redo the math:

Notice what drove the problem: 8 feet of elevation plus a 75-foot supply run on undersized pipe. The kit's ¾" mainline and barbed valves add almost nothing to the head budget — it's the supply pipe and elevation that matter. This is why the supply pipe diameter is the biggest lever you have for controlling friction loss.

This is exactly the kind of calculation our drip system sizing guide and its interactive calculator handle automatically — it runs all of this in real time as you adjust your inputs.

Greywater vs rainwater — why the pump type matters

Greywater and rainwater look similar on paper — both are water, both need moving through a system. But they have meaningfully different characteristics that affect pump selection, and using the wrong type causes early failures.

Greywater characteristics

• Contains hair, lint, soap residue, skin cells, and fine organic particles
• Temperature varies — warm to hot from showers, cold from laundry rinse cycles
• pH typically 6–9 but shifts with detergent type and usage
• Biologically active — can develop odor and bacterial growth within 24 hours if left standing
• Produced in frequent, irregular pulses (shower, laundry cycle) rather than continuous flow

What this means for pumps: greywater needs a pump designed to handle soft solids — lint and hair in particular. Standard clean-water centrifugal pumps clog quickly. Cheap sump pumps have seals and materials not rated for the chemistry or temperature variation. You need either a purpose-built effluent pump rated to pass ½"–¾" solids, or an integrated system like the Aqua2use where the pump is selected specifically for the application after multi-stage filtration handles the bulk of the solids load.

Rainwater characteristics

• Much cleaner than greywater — primarily roof surface particulates, dust, and organic debris
• Stored for hours to months in cisterns — stagnation and algae growth are risks in warm climates
• Consistent temperature, typically close to ambient
• May need higher head pressure if serving indoor non-potable fixtures (toilets, laundry)

What this means for pumps: rainwater systems can use a wider range of pump types, including standard centrifugal pumps, jet pumps, and booster pumps, because the water is cleaner and the chemistry is simpler. The main considerations shift to pressure requirements and storage management rather than solids handling.

Pump options — DIY and integrated systems

For greywater: effluent pumps (DIY approach)

If you're building a greywater system around a custom surge tank and separate filtration, effluent pumps are the reliable workhorse choice. These submersible pumps are engineered for dirty water, rated to pass ½"–¾" solids, and designed for continuous-duty operation. Well-regarded options include:

• Goulds WE05 / WE10 series — widely available, excellent solids handling, good track record in residential greywater setups
• Liberty Pumps 250 series — compact, quiet, good for smaller surge tanks, popular with plumbers
• Zoeller M53 / M57 — heavy-duty cast iron construction, long-lived, often specified for commercial installs
• Little Giant WRS / 6-CIA series — common in smaller residential setups, good value

Budget $150–$400 for the pump itself. You'll also need a properly sized surge tank (typically 20–50 gallons for residential use), dual float switches, a GFCI-protected electrical circuit, and some way to manage the 24-hour purge requirement. You're assembling a system from components, which gives you flexibility but also means every compatibility decision is yours to make.

For greywater: integrated systems

Integrated units like the Aqua2use combine the pump, multi-stage filtration, Electronic Pump Controller, surge tank, and overflow protection in one certified assembly. The pump is purpose-matched to the specific tank size and flow requirements — no compatibility guesswork required.

Two models are available from Water Wise Group:

Need to replace just the pump? Replacement pump packs are available — no need to replace the full unit.

If you need to replace the pump in an existing Aqua2use unit without replacing the whole system, replacement pumps are available separately.

The GWDD Pro during installation — the tank is set at slab level so the lid sits flush with finished grade.

For rainwater: pump options

Because rainwater is cleaner and typically stored in larger cisterns, you have more pump choices:

• Jet pumps (Grundfos JP series, Red Lion RL-SWJ) — self-priming centrifugal pumps, usually paired with a small pressure tank. Good for pressurized hose bibs and indoor non-potable fixtures like toilet fill valves or laundry.
• Multistage submersible boosters (DAB E.sybox, Walrus HQ series, Grundfos CM) — compact, can deliver higher pressure, some include built-in variable frequency drives that adjust speed to match demand. Ideal for indoor fixture pressure requirements.
• Small submersible utility pumps (Goulds LSP03, Little Giant WRS series, Wayne CDU series) — simple, low-cost, appropriate for low-head irrigation from rain barrels or small above-ground cisterns. Not suitable for any significant head pressure.

For rainwater irrigation specifically, a properly sized submersible with a float switch and a 24-hour auto-cycle timer handles most residential applications well. If you're connecting to indoor fixtures, you'll need a pressure-tank-backed system with adequate head for the fixture requirements — typically 30–60 PSI for standard fixtures.

Pump controls

A pump without proper controls will either run dry — which destroys the motor — or let the tank overflow. Understanding the control options helps you evaluate any system design.

Float switches

The basic on/off mechanism for most DIY greywater setups. A high float turns the pump on when the tank fills to a set level; a low float turns it off before the pump cavitates on an empty tank. Simple, reliable, and inexpensive — but no intelligence about the 24-hour purge requirement.

Most DIY setups pair float switches with a separate 24-hour timer set to force a pump cycle once per day. The problem: power outages reset most plug-in timers to 12:00, meaning after any interruption the system no longer auto-purges on schedule. Left unnoticed, water sits in the tank and develops odor and bacterial growth.

Electronic Pump Controller (EPC)

The Aqua2use uses an EPC instead of simple floats. The EPC monitors water level via magnetic micro-floats and is programmed to override the high float at least once per 24 hours — even if the tank hasn't filled. This guarantees the tank empties fully on low-greywater days and eliminates stagnation without a separate timer.

Critically, the EPC uses elapsed-time logic rather than a clock. A power outage doesn't reset it to 12:00 — it simply resumes counting from where it left off. For a system that's supposed to run unattended, this reliability matters.

Smart controllers

Some rainwater systems integrate with whole-home automation platforms. Generally overkill for greywater, where the primary requirement is reliable daily purging rather than sophisticated scheduling. If you're running a large rainwater system with multiple zones and seasonal variation, a smart controller can optimize dosing schedules, but it's an add-on to a well-designed base system rather than a replacement for it.

Electrical requirements

Both greywater and rainwater pump systems have the same core electrical requirements. These aren't optional — they're code in virtually every jurisdiction:

• Dedicated 110V/20A circuit: The Aqua2use GWDD draws 1.2A and the Pro draws 4.2A — modest by themselves, but a shared circuit creates risk of nuisance tripping and makes it harder to diagnose problems. Most permit applications require a dedicated circuit.
• GFCI protection: Ground Fault Circuit Interrupter breakers are mandatory anywhere a pump operates near water. This is non-negotiable for both code and safety — a standard breaker won't catch the kind of fault a wet pump can create.
• Surge protection: The Aqua2use installation manuals specifically recommend a surge protector on the outlet. Pump motors are vulnerable to voltage spikes from storms and grid fluctuations, and a $20 surge protector is cheaper than a pump replacement.

The electrical work is typically the simplest part of the installation — one dedicated circuit run from the panel, one GFCI outlet within reach of the unit. Have a licensed electrician do it. In most states the greywater permit specifically requires licensed electrical work, and for good reason.

Costs and lifespan

Upfront pump costs

• DIY effluent pump: $150–$400 for the pump. Add a surge tank ($100–$300), float switches ($30–$80), and electrical controls if building from scratch.
• Aqua2use GWDD: Full integrated system — pump, tank, filtration, EPC, overflow protection all included. One purchase, one installation.
• Aqua2use GWDD Pro: Higher investment for the larger pump, bigger tank, and underground installation design.

Operating costs

Greywater pumps run in short bursts — typically 1–12 cycles per day depending on household size and unit capacity, each cycle lasting 30–60 seconds. Annual electricity cost is minimal. At $0.15/kWh:

• GWDD (288W): running 20 minutes/day = ~35 kWh/year ≈ $5/year
• GWDD Pro (1,008W): running 20 minutes/day = ~122 kWh/year ≈ $18/year

Electricity is not a meaningful cost factor in greywater pump selection.

Lifespan and maintenance

• Quality effluent pumps in well-maintained systems: 5–10+ years
• Aqua2use Matala pumps: designed for continuous duty and come with a 12-month warranty from Matala.
• Filter media: cleaned (not replaced) every 4–6 months for the GWDD, 6–12 months for the Pro. The Matala foam filters are designed to be cleaned over and over, not swapped out.
• If a pump does fail: replacement pumps are available separately — you don't need to replace the whole unit.

Ready to take the next step?

The pump decision is really about matching your household's greywater output, your site's elevation and pipe distances, and your irrigation demand into a single coherent system. Most residential installs land squarely on either the GWDD or the Pro depending on home size and plant count.

Once you've settled on a pump, the next question is how to size the drip system around it — pipe diameters, emitter spacing, mainline length, and how many plants each unit can realistically serve. Our irrigation sizing guide covers all of that, and includes an interactive calculator that runs the full TDH and friction calculation in real time.

Frequently asked questions