HHD and Water Treatment

While the water in your home might be safe to drink, it is not safe to use for your home hemodialysis treatments. For this reason, you must have a water purification system either built into your home dialysis equipment or in addition to your home dialysis equipment so that the water you use for your dialysis treatments is ultra pure.

Why isn’t my faucet water clean enough for home hemodialysis?

There are many opportunities for water to pick up environmental substances starting when rain drops fall down to earth. Gases such as carbon dioxide can be picked up by the rain, dissolve and make acid rain. Once water seeps down into the earth, it can pick up numerous minerals including calcium from limestone, metals such as lead and copper and even poisons such as arsenic. There are man-made impurities that can contaminate the water such as pesticides and fertilizers. Well water often contains a large amount of salt, while water from reservoirs usually harbors bacteria, viruses and algae. And finally, city water suppliers add chemicals to water to destroy bacteria, fluorides to prevent tooth decay and aluminum to make the water clear.

While all this sounds a little alarming, tap water is safe to drink because it goes through a treatment process. The Environmental Protection Agency (EPA) sets standards for levels of impurities so that water stays safe to drink. Every public water system in the U.S. must follow this law which is called the Safe Drinking Water Act. However, much more “cleaning” is required to make water safe for dialysis, and standards for when water is considered ultra pure are set by the Association for the Advancement of Medical Instrumentation (AAMI). Centers for Medicare and Medicaid Services require dialysis providers to ensure that the water used for dialysis meets AAMI standards. Water for dialysis has to be free of even trace amounts of impurities that may find their way into tap water. Water for dialysis needs to be ultra pure

Why does the water I use for my dialysis treatments have to be ultra pure?

The thin, hair-like threads inside your dialyzer are hollow. The walls of these fibers are made of a semipermeable material which acts like a filter. During your dialysis treatment, your blood flows inside these hollow fibers, while the outside of the fibers is bathed in dialysate. Dialysate is a cleansing solution which is a mixture of water and chemicals that pulls the wastes and extra fluid through the fibers and out of your blood. However, because the fibers are semipermeable, if the water used to make the dialysate is not completely pure, impurities from the water in the dialysate can get into your blood. Many of these impurities can cause you serious harm.

If anything less than ultra pure water is used during your dialysis treatment, a variety of things could happen:

  • Too much calcium or magnesium can cause nausea, vomiting, muscle weakness, severe headaches, skin flushing and low or high blood pressure. 
  • Metals can cause a variety of symptoms including liver damage, inflammation of the pancreas, destruction of red blood cells, seizures, brain damage and even death. 
  • Pesticides and fertilizers can cause headaches, dizziness, convulsions and heart and liver damage.
  • The chemicals added to destroy bacteria will destroy red blood cells if they enter the blood stream. 
  • Bacteria and endotoxin can cause infections and fever. 
  • Overexposure to fluoride can cause abnormal hardening of bones, as well as nausea and vomiting, muscle twitching, low blood pressure and seizures.

How is fresh drinking water turned into ultra pure water for dialysis?

Currently, there are two water purification systems on the market. One is relatively new and is called the PureFlow SL DI system. This system comes with the NxStage home dialysis machine. The other is a portable reverse osmosis (RO) system which can be used with any dialysis machine.

The NxStage PureFlow SL DI system

The NxStage PureFlow SL DI system has been designed to bypass the obstacles of an RO system. Its water purification system, which is about the size of a standard end table, consists of the following parts:

  • a sediment filter which removes large particles from the water
  • a ultraviolet light tray which kills bacteria and breaks down chemicals in the water
  • a carbon filter which adsorbs chemicals in the water
  • a dual bed DI resin which removes dissolved electrolytes
  • a mixed bed DI resin as a back up and safety net to the previous DI Resin
  • an ultrafilter to remove bacteria
  • a 0.2 micron filter which removes any bacteria that may have been introduced into the system so it will not reach the patient

The PureFlow system has the advantage of using less water than an RO, only about five gallons per treatment. So, no special plumbing requirements are needed. And, if your well water is unsuitable for preparing ultra pure water or if you are living in a dry region and depend on water being delivered to your home, the NxStage dialysis machine can be used with factory prepared, bagged dialysate, thus eliminating the need for water treatment all together.

The reverse osmosis (RO) system

The reverse osmosis (RO) system uses a pump to push water through a semipermeable membrane or filter which removes almost all of the contaminants including bacteria and viruses. Other parts of a portable RO machine include a carbon filter which absorbs the chemicals added by the water department and a sediment filter which traps large pieces of debris. If your water is very hard, a softener may also be installed which removes calcium and magnesium because these substances could damage the RO system.  

The RO machine produces two types of water: product water and reject water. The product water is the ultra pure water which enters the hemodialysis machine and is used to mix the dialysate for your dialysis treatment. The reject water contains the bacteria that was cleaned out of the water and is sent down the drain and discarded.

Using a home hemodialysis machine with a portable RO means that specific requirements must be met. The RO must be hooked up to a water source that delivers at least two gallons per minute. Likewise, the drain receiving the used dialysate from your dialysis machine and the reject water from the RO must also have a capacity of discarding at least two gallons per minute. Usually, a kitchen sink faucet and a shower drain will meet these requirements, so setting up your dialysis equipment will mean finding a location near that water source and drain. Another option would be installing additional plumbing in your home.

There are other things to consider when using an RO. If your waste water drains into a septic tank, the large amounts of water used during each treatment may quickly fill up your tank. Disinfecting your dialysis machine with bleach may kill the “good” bacteria needed in your septic system. The large amounts of water needed by an RO system will increase your monthly water bill. And lastly, if you are on well water and the water quality exceeds the contamination standards set by the Safe Drinking Water Act, the RO may not be able to produce ultra pure water, preventing you from performing home hemodialysis using a portable RO system.

How do I make sure my home hemodialysis water is ultra pure?

DaVita® policies and procedures outline testing requirements to ensure that the water treatment system in your home does indeed produce safe, ultra pure water which meets or exceeds AAMI standards. This test is done before the equipment is used for the first time and at least annually afterwards. Your treated water and the mixed dialysate will be tested in regular intervals, usually on a monthly basis, to ensure bacteria growth does not exceed the allowable, safe limits and that the disinfection schedule of your home dialysis equipment is adequate. To make certain that the carbon filters remove the chemicals from the water, you will be trained to test for this before you start each treatment if you use an RO machine, or after each new batch of dialysate is made if you use the NxStage PureFlow.


Turning tap water into ultra pure water for your dialysis treatments is essential to protect you from harm or injury. Your dialysis center’s biomedical technicians will ensure that your dialysis equipment functions properly and your training nurse will make sure you are well trained to operate the system and perform required safety tests. Your health care team can assist you with questions or concerns you may have.