A water-driven dosing pump runs on the water passing through it. That is what makes it so useful: no power, no wiring, and a dose that stays in proportion to the flow. It also means every litre that drives the pump carries whatever is in your supply. Bore sand, dam silt, organic matter, rust flakes and scale from older pipework all travel straight into the parts of the pump that do the measuring.
Fitting a filter upstream is the simplest and cheapest way to protect that equipment. This guide covers what debris actually does to a dosing pump, why a self cleaning filter suits dosing installations better than a cartridge, and how to choose, size and install the Twist II Clean filter.
What debris does to a water-driven dosing pump
Proportional dosing pumps such as MixRite, Dosmatic and AquaBlend use a water-driven motor piston linked to a dosing piston. The clearances inside are tight, and the seals are what hold the dose accurate. Manufacturers of water-powered pumps routinely warn that debris in the supply scores the piston and housing, and that is exactly what our service bench sees.
Once particles get inside, the problems tend to show up in this order:
- Seal and piston wear. Grit acts like sandpaper on seals and piston walls. Worn seals cannot hold the stroke, so the pump draws less concentrate than the ratio setting says.
- Dose drift. Under-dosing a water medication, a fertigation program or a sanitiser is often the first sign, usually noticed as concentrate lasting longer than it should, or results dropping off.
- Sticking valves and loss of prime. A grain of sand under a check valve can hold it open, letting the pump lose prime or allowing air into the line.
- Stalling and irregular strokes. Debris in the motor section can make the pump hesitate, run unevenly or stop altogether at low flows.
- Blocked orifices. Venturi dispensers rely on small, precise passages. A build-up of sediment changes the draw rate long before the passage is fully blocked.
None of this happens overnight, which is why it gets missed. The pump keeps clicking, the line keeps flowing, and the dose quietly moves away from what you set.
Why a self cleaning filter rather than a cartridge
Cartridge filters do the job when they are maintained, but in practice they create their own problems on a dosing line. Changing one means shutting off the water, which lets air into the system and often means purging and re-priming the pump afterwards. Cartridges cost money every time, so changes get stretched out, and a clogged cartridge starves the pump of the flow it needs to run properly.
The Twist II Clean is designed around those problems. A quarter turn of the top handle does three things at once: it reverses the flow so water passes from the inside of the element outwards, lifts the element to open the flush port at the base, and carries the trapped debris out through that port. The whole flush takes less than 20 seconds and the water stays on the entire time, so no air reaches the pump.
Because the element is stainless steel and cleaned in place, there is nothing to replace. When cleaning is that quick, it actually gets done, and that is the real advantage on a farm, in a shed or on a processing line where nobody has time for fiddly maintenance.
Choosing the right filtration grade
The Twist II Clean is available in four grades, each with a colour coded element so you can tell at a glance what is fitted. The table below is a starting point, not a rule. Your water source and the equipment you are protecting decide the final choice.
| Grade | Mesh | Element | Typical starting point |
|---|---|---|---|
| 600 micron | 30 mesh | Brown | Dam, river or channel water with a heavy organic load, or as a first stage ahead of a finer filter |
| 250 micron | 60 mesh | White | Bore and tank water carrying sand, and general irrigation lines |
| 150 micron | 100 mesh | Grey | General protection for dosing pumps on a reasonably clean supply |
| 105 micron | 140 mesh | Black | The finest grade we stock, for mains or good quality water where pump protection is the priority |
Two things are worth keeping in mind. First, a finer element traps more but loads up faster, so it needs flushing more often. On very dirty water, a coarse filter followed by a finer one can be easier to live with than a single fine filter that blocks every few hours. Second, always check the filtration recommendation in your dosing pump manual. Some pumps specify filtration finer than 105 micron, and if yours does, talk to our team about the best setup for your site.
Sizing the filter for your flow
We stock the Twist II Clean in two connection sizes:
- 3/4 inch: maximum flow of approximately 95 litres per minute (25 US gpm)
- 1 inch: maximum flow of approximately 148 litres per minute (39 US gpm)
Both are rated to 100 psi (7 bar). The maximum flow figures apply to a clean element. As the element loads up, the pressure drop across the filter rises, so choose a size that gives you headroom rather than one that runs at its limit. A filter working near maximum flow will cost you pressure, and water-driven pumps need adequate pressure and flow to run their motor reliably.
As a rule of thumb, match the filter to the inlet size of your dosing pump and check that your peak flow sits comfortably inside the rating. Please confirm the thread type for your installation with us before ordering. Larger line sizes are also available, so get in touch if your flow is beyond the 1 inch model.
Not sure which dosing pump you are protecting? Our guide to choosing a water-driven dosing pump compares MixRite, Dosmatic and Chemilizer by flow, pressure and dose rate.
Installing it correctly
A filter only protects what is downstream of it, so placement matters more than anything else.
- Fit it upstream of the dosing pump, after the isolation valve and before the pump inlet, with the flow arrow pointing towards the pump.
- Plan for the flush water. The flush port discharges at the base of the filter, so position it where that water can drain away safely or plumb the port to a drain.
- Leave access above the filter so the handle can be turned easily and the element can be inspected.
- Consider pressure gauges on either side of the filter. The difference between the two readings tells you when it needs a flush, instead of guessing.
- On a by-pass setup, fit the filter on the leg feeding the injector. See our by-pass fertigation setup for how that configuration works.
Because the filter sits before the injection point, the flush water is plain supply water. No medication, nutrient or chemical goes out of the flush port, which keeps cleaning simple and avoids wasting product.
How often should you flush it?
There is no single answer, because it depends entirely on your water. A practical approach is to start with a flush at the beginning of each day or dosing run on bore, dam or recycled water, and weekly on clean mains water. Watch how much comes out and how quickly the pressure drop builds, then adjust. If the flush water is clear every time, you can stretch the interval. If it is still carrying sediment, flush more often or step up to a coarser pre-filter.
With a flush taking less than 20 seconds and no need to shut anything down, it is easy to build into a start-up routine.
Where the Twist II Clean earns its keep
Poultry and livestock water medication
Medicators on bore and tank water are among the most exposed pumps we service. Accurate dosing of medications, vaccines and water line cleaning products depends on the pump holding its ratio, and a filter is cheap protection for an AquaBlend Xtreme, Chemilizer or MixRite installation. See our animal health solutions for more.
Nursery, greenhouse and field fertigation
Dam water, recycled water and long irrigation runs bring organic matter and silt into the system. Protecting the injector keeps the nutrient ratio steady and also helps keep drippers and emitters downstream clear. Our guide to fertigation with water-driven injectors covers injector selection and setup in more detail.
Wash-down and vehicle sanitising
Biosecurity wash-down points often draw from farm water supplies, and a dosing pump that drifts means a sanitiser applied at the wrong concentration. A filter ahead of the pump helps keep the dilution where the product label says it should be. Our article on H5 bird flu and farm biosecurity explains where dosing equipment fits into a biosecurity program.
Food processing and industrial dilution
The Twist II Clean is also used for lubricant, cutting fluid and coolant dilution, chemical delivery, and filling totes and drums. In each case, a dosing pump that stays accurate means consistent product concentration and fewer surprises on the line. See our processing and facility cleaning solutions.
Already seeing wear? Service first, then filter
A filter prevents damage, it does not repair it. If a pump is already drifting, stalling or losing prime, the seals and pistons may need attention. Our equipment servicing team runs and checks units under live water, and we carry spare parts for the brands we supply. Once the pump is back to specification, a Twist II Clean upstream helps it stay that way.
Frequently asked questions
Does the Twist II Clean need replacement cartridges?
No. The filter element is reusable stainless steel. It is cleaned in place by flushing, so there are no cartridges to buy or stock.
Do I have to turn the water off to clean it?
No. A quarter turn of the handle reverses the flow through the element and opens the flush port while the water stays on. The flush takes less than 20 seconds and no air enters the line.
Does flushing the filter waste chemical?
No. The filter is installed upstream of the dosing pump, so the flush water is untreated supply water. No chemical, medication or nutrient goes out of the flush port.
Which filtration grade should I use with a water-driven dosing pump?
Start with the finest grade your water quality and flow will tolerate without constant flushing, and check the filtration recommendation in your pump manual. If the manual calls for finer filtration than 105 micron, talk to our team about the best setup for your site.
What is the maximum operating pressure?
100 psi (7 bar).
Can the Twist II Clean be installed outdoors?
Yes. It is a rugged design, rated for installation indoors or outdoors.
Protect your dosing equipment
The Twist II Clean filter is available now in 3/4 inch and 1 inch sizes, with four filtration grades. If you are not sure which grade or size suits your water and your pump, call our team on (02) 4329 0905 or request a quote and we will help you match the filter to your installation.
