Water for healthcare facilities

Green Dialysis - Home Dialysis Patients Resource Conservation - Water

Basic water facts

Water is a precious and finite natural resource, but is under increasing threat.

Global water use has been growing at more than twice the increase rate of population during the last century.

An increasing number of regions are reaching the limit at which water services can be sustainably delivered.

Water shortages will be amplified by climate change, including in Australia, the driest inhabited continent on earth.

We therefore have a responsibility to use water carefully.


Current HD water use is careless, not careful.

Haemodialysis (HD) requires large amounts of ultra-pure water, usually generated by a process called reverse osmosis.

  • Mains water consumption for HD will vary depending upon machine type, reverse osmosis (RO) system, and treatment duration and frequency.
  • A typical “standard” 4 hour HD session draws ~500L of mains water.
  • 60-70% of this is routinely discarded to drain as reverse osmosis “reject” water, despite that reject water is still potable and potentially re-usable. At metropolitan or large regional dialysis centres, the typical volume of RO reject water sent to drain has been estimated at approximately 1 million litres per annum. This is equivalent to approximately half the amount of water contained within an Olympic sized swimming pool.


Opportunities for water conservation and reuse.

  1. Ask yourself whether RO reject water is re-used and/or recycled by your facility

If ‘yes’, check that re-use is occurring at all your dialysis sites (in-centre, satellite and home).

Reverse osmosis reject water re-use options should be considered for all haemodialysis sites, regardless whether hospital or community-based.

If ‘no’, ask the following questions!


  1. Do you understand what reverse osmosis (RO) is and how it works

If you do not, find out more about RO here.


  1. Make sure you understand the notion of RO reject water

The North West Dialysis Service has produced an excellent handbook on reusing and recycling RO reject water.

This handbook will teach you how to understand dialysis water systems.


  1. Confirm a timed estimate of the amount of RO reject water lost to drain.

Most engineering departments can easily and accurately measure your water loss.

But, if not, and your RO is accessible, collect and measure a 5 or 10 minute timed sample yourself ***.

  • For centralized RO systems, divide the composite drain volume by the number of collection minutes to estimate the average total volume of RW lost per minute to the waste drain.
  • Divide this volume by the number of machines active during a treatment session. This will estimate the mean loss per minute per machine. Multiply by each treatment length (minutes). This then estimates the RO reject water lost per patient, per treatment.
  • Where each haemodialysis machine has an individual RO system (e.g. home patients), first divide the collected volume by the number of collection minutes, then multiply by the treatment length (minutes) to reach an estimate of RO reject water lost, per patient, per treatment.
  • Do not forget that mains water is also used – and reject water generated – both during the pre-dialysis run-up and the post-dialysis rinse and sterilize periods. And do not forget the water losses during the inter-treatment ‘idle’ in facility services operating more than one session/day.
  • If possible, measure these inter-treatment losses too. Alternatively, use the reported literature run-up and rinse phases loss estimates of ~50 – 80L (mean = 65L) per machine per session + another 30L loss during the in-shift idle phase.
  • Finally, multiply the ‘all-loss’ total per machine by the total number of machines in use to estimate the total RW volume lost to drain.

*** Remember, a number of different RO systems exist, each with a different level of efficiency. It is therefore important to measure your specific RO system as volumes of RO RW will vary, system to system. It is wise to repeat your check, perhaps once a year.

An example:

  • The average Australian dialysis service runs a dialysate flow rate of ~500ml/min.
  • A 4-hour treatment thus requires 500ml x 60min x 4hr ≈120 L/treatment for dialysis fluid generation.
  • As most RO systems ‘reject’ approximately 2/3rd of the presented mains water, ~240 L will be lost as reject water.
  • Add all losses during run-up, rinse, disinfection and idle phases 

                   Water loss/treatment/machine = 240 L + 65 L + 30 L … or 335 L/single treatment

  • Total water use/treatment = 120 L (treatment process) + 335 L (water lost to waste) = 455 L with 60-70% of the total mains water draw of most dialysis services being salvageable and re-usable.
  • Asa RO reject rates and flow rates through dialysis machines are notoriously variable, doing your own measurements with your own equipment is important.


  1. Confirm the quality of the RO reject water you are wasting.

It is quite simple to sample reject water at the outflow port of any RO system.

  • Collect a sample in a sterile jar for biochemical and bacteriological water analysis. While you will be used to doing this for inflow water, few have ever bothered to sample and test the ‘quality’ of the RO reject water outflow. Most local water boards will provide this testing for free – or for a nominal charge.
  • Then … prove it to yourself: take the plunge … taste the reject water from your RO!
  • It will do you no harm.

The following analyte table shows a typical biochemical analysis of both mains and reverse osmosis reject water sampled from two separate RO systems in the Barwon Health Renal Service (2004).

All levels meet EPA standards for drinking ‘potable’ water (NB: a ‘✓’ vs. a ‘x’ in the far-right column denotes ‘complies’ vs. ‘does not comply’ with EPA standards).


Table: Water Biochemical Levels


Other than for a modest increase in conductivity (due to traces of residual salt(s) in the RO reject water) that imparts a slight metallic taste to the RO RW – RO reject is actually ‘betterthanmains’ water. Remember it has already been carbon-filtered, particulate-filtered and softened, where and when necessary.

If further proof is needed to convince your healthcare facility administration, you could do the following.

  • Analyse the biochemistry, turbidity, conductivity and bacteriological sterility of the RO reject water… they may simply not be aware that they are throwing away high quality water. Saving it will save them dollars!
  • Collect some water from a natural mineral spring.
  • Take several samples of the spring water and test-drink them against your RW water.  Better still… offer a ‘taste-test’ of the samples to your Board of Management. Show them just what they are wasting.
  • In 2003/4, Prof. Agar did exactly that. He asked the Barwon Health board members to each taste two samples … Sample A = reject water, Sample B = commercial mineral water.
  • As they were unable to identify which was which, his re-use program was funded – on the spot!


  1. Consider opportunities for RO reject water re-use.

Possibilities for re-using RO RW from a facility based system include:

  • To provide water for hospital laundries
  • To create steam for sterilization
  • As grey water in toilet facilities
  • In sanitation systems/janitor stations in wards
  • In low pressure boilers
  • For watering of onsite gardens
  • To provide water to nearby services, businesses, or parks – many would be grateful for access to reliable, low-cost (or free) water source.
  • Encourage the children of staff and/or patients to open a weekend, low-cost, car wash for the community using RO reject water … some money for the kids’ pockets, and a reuse option for the reject water.

Remember, unlike rain-dependent grey-water catchment(s), dialysis units provide steady and predictable supplies of high-quality RW, day in, day out, and all year-round.

By recycling and reusing reverse osmosis reject water in both at all its’ facilities, and at home in their large home HD program, Barwon Health, Geelong saves ~4.8 milion litres of water each year.


Re-using RO reject from a community-based service

While RO reject water re-use options should be considered by all and any haemodialysis facility, it can be more difficult to establish a reliable and secure demand for reject water re-use from community based facilities– especially in the wetter months of the year.

In past conditions of endemic drought, local councils, schools, and sporting organizations have been eager to arrange tanker collection of reject water to sustain parks, sporting grounds, landscaping, and vegetation areas.

In the wetter months, when there is less demand for discretionary water, other more sustainable re-use agreements are required.

  • Community dialysis services, if adjacent to, or within easy pipe-reach of a business requiring a reliable water source – e.g. parks, gardens, automotive services, car-washes, or other industries – should investigate the potential for RO reject water re-use… especially if the reject water is offered free. After all, it was previously just going down the drain.
  • Local service organizations may assist with set-up costs, especially if their water costs are reduced, or if advantage is taken of water-tank discounts and/or rebating schemes.
  • Explore whether plumber, electrician or other trade expertise is available ‘pro-bono’ from within the client base of the dialysis service itself. This may significantly reduce set-up costs.
  • Encourage positive media coverage of resource re-use – this helps to attract set-up funds, and provides useful ‘good news’ stories for the media.

In addition to any environmental benefits, these options (and others) can combine to significantly reduce healthcare expenditure on water.

  1. Perform a ‘purchase and installation’ cost analysis of the equipment required for RO reject water capture and reuse.

Your engineering department should be able to help you with this. You will need to consider the following equipment:

  1. A 2,000 – 2,500 L ‘holding tank’ at dialysis unit or ground level.
  2. A roof top storage tank, the size/number depending on your daily/weekly RW output and hospital size.
  3. An appropriate-sized pump for the distance/height required, and available from your local hardware store.
  4. A reverse float for the holding tank (a rising float arm as the holding tank fills should be set to trigger the pump action).
  5. A simple PVC pipe circuit to connect the tanks and the intended destination.
  6. The elevated storage tank can then gravity-feed ‘on demand’ (e.g. to the Central Sterilising Department or CSD).
  7. If RO RW production exceeds re-use the water demand of the primary destination, consider direct gravity-feed of RO RW to other destinations (e.g. ward toilet systems and/or janitor stations).
  8. Any remaining RO RW can be directed to garden and landscape use, and/or any other water uses that may be determined.


  • Local service organizations (e.g.: Lions, Apex, Kiwanis, or Rotary) may assist with costs. In addition, equipment and/or plumbing expenses may be reduced through hospital or healthcare wholesale discount agreements.
  • Beat the drum: ensure hospital administrators are aware they will benefit from reduced water costs. RO reject water re-use should be sufficiently cost effective to repay any capital investment within a few years (Barwon Health found the full return on investment took ~30 months, although the storage tanks were donated by local industry). Subsequent to recovery of investment, significant institutional budget savings then accrue, year on year, from further water saving.
  • If additional novel uses for RO reject water reuse emerge, share these discoveries. Blog about them, or email-share suggestions through this website … see the email and blog functions at the end of this website … we’d all love to hear about them
  • Consider submitting abstracts to national and international scientific meeting so that others can learn from you.
  • View details of the Australian and New Zealand Society of Nephrology (ANZSN) and Renal Society of Australasia (RSA) annual Environmental Research Prizes on the ANZSN and RSA websites.