Our Geomembrane Tankliners will last 30-50 years.

Install quality is everything for longevity, without replacing outlet fittings and correctly sizing (often upsizing) overflows the tank & Tankliner will not go the distance.
We always replace outlet fittings, valves and always pay very close attention to overflow set up and flow, where possible making improvements to the tanks we work on.

UV radiation kills plastics, fast.
In most tanks there is no UV getting to the Tankliner and as such the life span limiting factor is the quality of the plastic used & the methods used to weld, secure to the tank and seal through penetrations.

We use Stainless Steel fixings, compression bands for pipework penetrations and have our welding equipment set up with extremely precise heat controllers to ensure we have enough heat input to weld but no more.

Plastics continue to see incremental improvements and with the current advances in Polyethylene Geomembranes we expect to see our liners lasting twice what they would pre 2000.

We replace many PVC liners that fail shortly after the 20 year mark due the plastic becoming brittle and cracking, hence we steer well clear of PVC Geomembranes.

Yes, Polyethylene Tankliners are certified perfectly safe to drink from.
Certified no BPAs, no colour, taste or odour imparted on your water.

The Polyethylene Geomembrane stock we using is certified to AS/NZS4020:2005 to NOT impart any taste, colour or odour to water.

We have on file all of the relevant testing documentation and are happy to copy these documents through.

An excerpt from testing completed by AWQC:
“The results presented herein demonstrate compliance of Permaflex fPE, Black Flexible Polyethylene to AS/NZS 4020 when exposed at area to volume ratios up to 15000 mm2/L at 60°C ± 2°C. Lining thickness to include 0.5 mm to approximately 1.5 mm.”

Primarily Tankliner fabrication and installation as a full service. This is the bulk of our business and we are heavily invested in specialised tooling & equipment for this work.

We also have a large amount of experience in all things relating to potable water supplies: pumps & filtration, automation, control & telemetry systems for water/water treatment systems with experience in everything from domestic systems to industrial plants.

We fabricate everything we install. This gives us the advantage of customising each Tankliner to each particular tank.

We’ve developed unique methods and custom tooling for both our fabrication & installs allowing us to provide the best product on the market while still providing the best value proposition available.

This also means we hold excess stock to cover weeks of work at a time enabling quick turnaround times when stuff hits the fan.

We bring the kitchen sink of tools and fittings to each and every job meaning we (almost) always run to schedule.

Out of 500+ installs to date only once have we had to delay the refill of a clients tank overnight.

All areas of wider Auckland, we also travel for jobs all around the country

We are regularly working in the following ares: Beachlands & Maraetai, Whitford, Clevedon, Ardmore, Hunua, Buckland, Tuakau, Waiuku, Pukekohe, Pukekawa, Karaka, Franklin, Kumeu & Waimauku, Riverhead, Coatesville, Rural Albany, Dairy Flat, Stillwater, Whangaparaoa, Army Bay, Stanmore Bay, Tindalls Beach, Arkles Bay, Mahurangi East, Mahurangi West, Leight, Pakiri, Warkworth, Puhoi, Waiheke Island.

We are happy to travel a bit further out for jobs and have many jobs completed in Northland & the Far North, Coromandel, Waikato, Bay of Plenty, Hawke’s Bay, Taranaki, Manawatu, Wellington, Great Barrier Island, South Island from the Sounds to Invercargill.

Yes, a leaking concrete water tank can be repaired using a geomembrane liner without replacing the tank.

We’ve put Tankliners in tanks with multiple golf ball sized holes in the side that are still standing to this day. The tanks have to be in a seriously bad way before a Tankliner is out of the question.

We value our time and want to see our work go the distance, we’ll be brutally honest if we think your tank isn’t worth spending money on.

Give us a call now if you want to discuss further!

https://www.membranedynamics.nz/get-a-quote-asap

For a “standard 5000 gallon tank” in Aucland - $2800 +GST or ~$3200 inclusive of GST supplied and fitted inclusive of the tank clean, replacement pipe fittings and valves as of April 2026.

Most domestic tanks we see in the 20-40 year old range are a “standard 5000 gallon” or about 22,500 litres - approximately 3.45m diameter and about 2.65m internal height.

This includes empty & clean of the tank, replacement outlet fittings, isolation valve & refit to existing pipework, pressure sealed overflow pipework through sidewall of the Tankliner & refitted to overflow pipework outside of the tank.

We work on a fixed quote basis and will always quote any additional bits and pieces required upfront such as additional sidewall penetrations for inlets/balance pipes, internal suction pick ups etc.


Cuboid tanks can require a bit more input to accurately price - as an example a 48000L tank measuring 6.00mL x 4.00mW x 2.00mH with 1× 100mm overflow penetration & replacement outlet fittings would cost approximately $4200 +GST installed.
Current as of April 2026.

For tanks up to 30,000L we complete most installs in under 5 hours and often have a water truck turn up soon after we leave.

We pre fabricate all of our Tankliners (usually done 1-10 days prior to install).

On the day we turn up at 8am to start work, we will usually have the tank empty and clean with all of our prep work done by 10am, this includes drilling & coring for replacement outlet fittings, overflows and refitting of pipework for the pump outlet.

The Tankliner is then lowered into the tank to start fitting which will take 1-2 hours on most jobs.

Once the Tankliner & all pipework is fitted off we will set epoxy mortar gaskets to lock pipework in place, tidy up the site and be out of there by 1pm.

We often book in water cartage for clients for any time after 1pm on the day and rarely do we run later than this on 20-30,000L tanks.

Pumps can be turned back on as soon as there is water in the tank.

The plastic itself will have no effect on the water held in your tank.

One effect of the Tankliner however is that it will isolate your water from the concrete or plaster surface of your tank.
Over time rainwater, when sitting in a concrete or plaster tank, will pull carbonates from the plaster or concrete to balance pH inside of the tank.

This is usually the reason your tank is leaking as it no longer has enough binder to the tank to isolate the steel reinforcing from water, allowing the steel to oxidise and rust jack, creating cracks.

This is of course also the case if you are looking to replace with a plastic tank.

We can supply and install pH neutralising filters on the pressure side of your pump to raise pH as it goes into a dwelling if this is of concern. pH neutralising filters use a calcium carbonate of a certain grain size as a sacrificial media to raise pH (and hardness) slightly as water passess through. These filters require media top ups at 12 months intervals.
We use either Calcite or Akdolit media for these pH neutralising systems.

No, our Tankliners can sit dry for extended periods awaiting rainfall.

Certain systems will require an immediate refill such as below ground tanks where groundwater has the potential to float a tank if the water table rises rapidly.

Unfortunately we cannot store the water in the interim and any water that we cannot move to any adjacent tanks will be discharged to waste.

The cost in labour to transport, set up, pump into & pump back out of a temporary storage tank exceeds the cost of a bulk water delivery in almost all cases.

We’ve seen clients try every trick in the book, a wedge of dry kindling forced into the crack is the most effective way to stem the flow.

If you still have some water in the tank and the leak is from one or two single cracks on the tank, a small wedge of dry kindling driven into those cracks from the outside can buy you some time.
The kindling wedge will expand slightly as it takes on water and is the only method we’ve seen that works reliably as a stop gap measure.
It won’t affect us much with the install of a Tankliner as any crack of that size we would cover or fill before the Tankliner goes in.

Give us a call ASAP - we do keep a range of Tankliners in different common sizes on hand for these kinds of events.

We’ve had phone calls at 5pm, picked up the tools to head to site and been out of there by 11pm allowing clients to have water on as soon as the tanker truck arrives the next morning.

We don’t charge penalty fees for urgent work unless there’s a significant additional time cost on our end in getting back to the workshop, much of what we do is urgent.

Nothing to the tank itself.

It’s always wise to turn the pump off before emptying the tank, we will do this if we can access the pump, otherwise we will make sure cleint or tenant has the pump off before we start work.

Always a good idea to fill up a few buckets just in case you need to flush the toilet etc.