This is due to water bypassing around the non-return valve (NRV) at the bottom of the dispenser.  On all units (Series 1 and 2) the dispensate hose plugs into a tapered nut, which is the seal for the non-return valve.  If foreign particles build up on the seal on the inside of the nut or the non-return ball is unable to seal properly, then the dispensate drum will back fill.

For all Se-Tech dispensers identification and repair is straight forward:

  • Bypass the water supply around the dispenser
  • Ensure the tapered nut can be seen (on Series 2 dispensers set dosing rate to 1)
  • The hose is a friction fit to the nut, simply pull it out
  • Unscrew the nut (hold the body immediately above when doing so)
  • Inside the NRV there is a stainless steel weight, a ball (that does the sealing) and an o-ring fitted to the inside of the nut

If backfilling, there is leakage either between this o-ring and ball, or between the o-ring and nut.

  • Clean out any build up or material on the o-ring and/or ball.  Both must be clean in order to seal properly
  • Check the o ring is seated properly into the nut
  • Check the ball is clean, round and in good condition
  • Confirm the flat side of the weight is clean, without pitting or product build up

Reassemble the NRV

  • Weight goes in first, cross up (i.e. flat side to the ball)
  • Ball goes in next
  • Screw the nut containing the seal o-ring in place: HAND TIGHTEN ONLY

Over tightening may cause damage to either the NRV nut or body, requiring replacement.

Check the drum isn’t back filling – see “The Dispensate Drum is back filling” above.

If your dispenser is a Series 2, the NRV is the only user serviceable component: please contact us to discuss or arrange a service.

If your dispenser is a Series 1, the issue is most likely a worn concentrate seal or a non-functioning stop valve in the T-Bar. See the exploded diagram for the location of each of these components.

  • The concentrate seal should be unworn – i.e. have a smooth taper on the outside surface without a step. See here to identify a worn vs good concentrate seal.
  • Confirm the stop valve is clean and seals well against its seat, and that the hole through the T-Bar underneath the stop valve is clean and clear
  • Unscrew the adjuster assembly from the bottom of the dispenser and confirm the inside of the stainless steel (‘adjuster’) tube is unpitted and free of product build up. This is the surface the concentrate seal runs up against, and so there must be a good fit between the two component to generate suction
    • If product buildup is evident, clean the adjuster tube in warm (not hot!) water using a bottle brush and a cleaning product such as ‘Dynamo’ or dishwash liquid
    • If the interior of the tube is pitted, replacement is required: the adjuster tube part number is 3228. Please see here for a parts list of the Series 1-32 dispenser.
This is most likely due to a worn main valve. See the exploded diagram for the location of this component.

To check:

  • Bypass water around the unit and remove the piston assembly
  • There should be no more than 0.3mm clearance between the main valve guides and the inside of the piston (check this using feeler gauges)

Should wear be greater than this, one or both of these parts will need repair/replacement: please contact us to arrange a service.

Excessive water flow / pressure can in some cases result in broken main valve spring; confirm your water pressure and flow is less than 210 PSI and 6000 l per hour.

  • A drum lid stops foreign objects such as dirt or leaves getting into the container, which could block the filter, or if sucked into the system, will cause wear on your dispenser and downstream components such as valves, ball cocks etc
  • Rainwater will dilute your mix, which will affect your dose rate
A 2-drum mixing setup reduces the abrasive and undissolved particles going through your dispenser and downstream components, maximising seal life and minimising wear.

  • We recommend mixing your additives with water in the mixing drum and leaving until dissolved (1 to 24 hours depending on water and additives)
  • When refilling the dispensate drum the solution is drained from the mixing drum into dispensate drum, leaving the heavy abrasive non-dissolved material behind. Some of this material over several mixings will dissolve and be used – dump out the heavy non-dissolved stuff periodically as appropriate
Different mixes of chemicals and water supply types can result in high electro-negativity build up which “picks” the chrome and nickelCorrodedNRVWeight from stainless steel, and rots brass, copper and many other metals. This was a stainless steel NRV weight from a unit without a passivator:

The Se-Tech zinc passivator is made of more than 99% pure zinc. This acts in the same way as a block of zinc bolted to a boat keel or an outboard motor, and will decay in preference to the materials in your dispenser and pipe fittings.

We recommend checking your passivator weekly: if you observe decay order a replacement.

Please Note: “Ordinary” cast or galvanised zinc products often contain cadmium and other products which may adversely affect animal health.
We recommend using only the Se-Tech zinc passivator.

Under normal conditions a zinc passivator should last greater than 6 months. Some farmers have found that earthing their dispenser  reduces the corrosion rate. For recommendations please Contact us.
Please note that whilst we recommend pre-filtration for optimal equipment life in poor quality water situations, the Series 2 dispensers with their heavier seals and continuous wiping capability, will significantly out perform the series 1 dispenser.

  • The filter in the manifold is a coarse filter, intended to stop twigs, pebbles etc from entering the dispenser. It will not stop silt, iron sand etc
  • If large particulates are still passing the filter we have available a finer filter which may be of assistance. Please note that when using a finer filter it will be necessary to clean out the filter more regularly
  • Please note when using river / stream water, rain after a long dry period will likely cause an increase in silt which is extremely abrasive. The use of your dispenser in these conditions will significantly increase wear and impact reliability
  • Firstly confirm water is flowing through the dispenser.
    • Open a tap downstream from dispenser, confirm that water is flowing and check if the dispenser cycles
    • If there is little flow, check and clean the “Y” filter in the dispenser manifold (the last component before the quick release coupling at dispenser entry)
  • If you have recently upgraded your pump / lines / water system, confirm that flow and pressure are still within the ratings for your dispenser. Manuals and specifications are found here: Series 1-32 Series 2-32 Series 2-50
  • Check the dispensate suction hose filter is clean and not clogged
  • Has the dispenser been dismounted / serviced recently?
    • If yes, alignment could be a problem
      • Dismount the dispenser and place on a flat surface. If the dispenser “rocks” on its mounting brackets then it is out of alignment, which may cause jamming. We suggest Contacting us
      • If it doesn’t “rock” (while still on the flat surface) put a square against the quick release coupling entry and then the exit: these should be at 90 degrees from the dispenser mounts. If not, the dispenser has become twisted and will require realignment – Contact us
  • If your unit is a Series 1 dispenser and the piston assembly is locked at the bottom:
    • There may be a build up of product in the adjuster tube – the concentrate seal may be locked into this. See checking the adjuster tube under the “Dispenser is not sucking” topic above
    • If you have disassembled the piston assembly recently, the T-Bar may be misaligned. Contact us
  • If your dispenser is “bouncing” or “hovering” at the top of its stroke
    • firstly confirm water flow as above
    • confirm the suction hose filter is clear – if blocked, there may be damage to the dispenser’s stop valve.
    • Your main piston seal (or if a Series 1, additionally the clear cylinder) may be worn, allowing water to bypass around the outside of the piston assembly. Please Contact us

There are 2 reasons for this to happen: either

  • you have no or very low water flow – the 32mm unit requires at least 5 L per minute to operate, the 50mm unit requires 10 L per minute, or
  • something has been sucked into the dispenser and has jammed the unit. If you have a Series 1 unit you can check this out yourself or send it into us. If you have a Series 2 unit send it in to us and we will check it out for you