Water for healthcare facilities

First ask some questions about your healthcare facility.

  1. Does your healthcare facility have on site gardens?
  2. Are there any nearby services, businesses, or parks that might appreciate a reliable, low-cost (or free) water source?
  3. Does your facility operate a nearby Central Sterilizing Department (CSD)?

If the answer is ‘yes’ to any or all of these, ask three further questions.

  1. Do you know how what Reverse Osmosis (RO) is and how it works?
  2. Do you know what RO reject Water (RW) is?

If not, there is a good explanation of this given by Wikipedia. It might be worth reading this before going on.


  1. Is Reverse Osmosis (RO) reject water (RW) re-used and/or recycled by your facility?

If ‘yes’, is this occurring at all your dialysis sites (in-centre, satellite and home)?

If ‘no’, consider taking the following steps:

  • Measure and confirm a timed estimate of the amount of RO RW lost to drain. Most engineering departments can easily and accurately measure this but, if not, and your RO is accessible, collect and measure a timed sample yourself (eg: a 5 minute collection).
  • 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. Dividing this volume by the number of machines active during a treatment session estimates the mean loss per minute per machine. Multiplying by each treatment length (minutes) then estimates the RO RW lost/patient/treatment.
  • Where each haemodialysis machine has an individual RO system (eg: home patients), divide the collected volume by the number of collection minutes, then multiply by the treatment length (minutes) to reach an estimate of RO RW lost/patient/treatment.
  • Do not forget that mains water is also used – and RW is generated – during the pre-dialysis run-up + post-dialysis rinse and sterilize periods, as well as during inter-treatment idle phases in facility services operating more than one daily session.
  • If possible, measure these inter-treatment losses too, or use the reported literature which estimates an additional ~50 – 80L (mean = 65L) is lost/machine/session during run-up and rinse phases and another 30L is lost during the between-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.

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 ≈120L/treatment for dialysis fluid generation.

As most RO systems ‘reject’ ~2/3rd of the presented mains water, approximately twice this amount (240L) will be lost as RW.

Add the additional losses during run-up, rinse, disinfection and idle phases, and the water loss/treatment/machine is approximately:

240L + 65L + 30L = 335L for a single treatment

The total water use/treatment = 120L (treatment process) + 335L (water lost to waste) = 455L.

This suggests that >70% of the total mains water draw of most dialysis services is salvageable and re-usable.

Do these calculations for yourself at your service.

Remember, though, all reverse osmosis systems vary in their reject rate.

In addition, flow rates through dialysis machines – though assumed to be accurate – are notoriously inaccurate.

So, doing your own measurements, with your own equipment, is important.

BUT, as the weekly, monthly or yearly volume of wasted RW can be profound, be prepared for a shock!


  • Confirm the quality of the RO RW you are wasting.It is quite simple to sample RW at the outflow port of your 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 RW outflow.

Note: Most local water boards will provide this testing for free – or for a nominal charge.

Prove it to yourself: take the plunge … taste the reject water from your RO!

The water will do you no harm.

The below table shows the biochemical levels of water taken from both mains water and reverse osmosis reject water in our unit at Barwon Health.  It can be seen that the levels meet EPA standards for drinking water.

Other than a moderate increase in conductivity – due to the low residual salt concentration that the RO process is designed to remove from mains water – it is actually ‘better-than-mains’ water as it has already been carbon and particulate filtered and softened!

If you need further proof to convince your healthcare facility administration, do the following.

  • Analyze the biochemistry, turbidity, conductivity and bacteriological sterility of the reverse osmosis RW… they may simply not be aware that you are throwing away high quality water. Saving it will save them dollars!
  • One useful exercise, should any doubt remain, is to 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, at Barwon Health, we did exactly this, and our re-use program was funded – on the spot!
  • Once convinced that RO RW is actually high-quality water… consider the ways it can be saved, and then the many options for re-use.

How to Save/Re-use reverse osmosis RW from a facility based system

Hospital administration should consider installing storage and feed systems to redirect the dialysis RO RW for CSD steam production.

Perform a ‘purchase and installation’ cost analysis of the following equipment.

  1. A 2,000-2,500L ‘holding tank’ at dialysis unit or ground level.
  2. A roof-top storage tank, the size/number depending on your daily/weekly RW output.
  3. An appropriate-sized pump for the distance/height required.
  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 PVC pipe circuit to connect the tanks and the intended use destination.
  6. The elevated storage tank can then gravity feed ‘on demand’ (e.g. CSD).
  7. If RO RW production exceeds re-use destination water demand, consider direct gravity feed of RW to other destinations (e.g. ward toilet systems and/or janitor stations).
  8. Any remaining RW can be directed to garden/landscape use, and/or other water uses.


  • If additional novel uses emerge, share the discovery, submit abstracts to national and international scientific meetings… we’d love to hear about it!
  • Local service organizations (Lions/Apex/Rotary) may assist with costs. In addition, equipment/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. RW re-use should be sufficiently cost effective to repay any capital investment within a few years.
  • At our institution (Barwon Health) the full return on investment (RoI) took ~30 months, although the storage tanks were donated by local industry.
  • Subsequent to RoI recovery, significant institutional budget savings then accrue, year on year, from further water saving.

How to re-use reverse osmosis RW from a community based system

Reverse osmosis RW can be reused and re-use options should be considered by all and any haemodialysis facility.

Unlike rain-dependent grey-water catchment(s), dialysis units provide steady and predictable supplies of RW year-round.

But, while reliable and regular RW volumes are generated, it can be difficult to establish a reliable and secure demand for RW use – 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 RW to sustain parks, sporting grounds, and landscape 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 – eg: parks, gardens, automotive services, car-washes, or other industries – should investigate the potential for RW re-use… especially if the RW 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 rebate schemes.
  • Explore whether plumber, electrician or other trade expertise is available ‘pro-bono’ from within the client base of the dialysis service.
  • 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.

While we have not explored all these avenues – each service is different and may find and develop different solutions – these are examples of the sorts of steps that any unit can explore, and implement.

Recycling RW through the RO – ‘continuous looping’

This is primarily a technique to consider in home dialysis if/when water is scarce.

See section on water conservation for home dialysis patients.