Questions and Answers about Infestation in Water

Most of this information is based on information from Vaad Lekashruth Hamayim, the O.U.and Rabbi Jacob Lach.

What type of infestation is present in New York City Water?

Copepods are present in New York City tap water. The primary species that is found in the water―begins life measuring about 90 microns (there are 25, 400 microns in an inch), and grows to about 800 microns (in males) and 1400 microns (in females) in about five weeks.

Other species are present as well


What is the source of the infestation?

The organisms that are found at the tap come from the reservoirs. (At one time, it was believed that the organisms came from the water mains, but research has shown this to be false.

Isn’t the water filtered?

Isn’t the water supply filtered? No! New York City is exempt from the federal and state requirements of municipal water supply filtration. The water need not be filtered. Drinking water is drawn from the reservoirs, and aside from the addition of chlorine and fluoride, the water arrives at the tap the way it left the reservoir.

In 1994 and 1995 the Department of Environmental Protection made studies of the copepod population of the reservoirs. These studies found copepods in all of the reservoirs.

Which Reservoirs Are Involved?

The copepods have been found to live in all of the reservoirs that supply New York City.

There are 7,400 surface water systems in the United States, of which 7,310 have filtration plants. Municipal filtration, if properly maintained, will successfully remove copepods and related organisms from the water, to a level acceptable in halachah. Of the 90 systems that do not filter their water, most serve a very small population. Aside from New York City, Syracuse and Seattle are examples of large cities whose water supplies are (at least in part) not filtered.


What level of infestation is found?

The Department of Environmental Protection has confirmed that copepods are present in significant quantities throughout the water of New York City. The level of infestation varies from place to place. At one testing of 18 samples taken by the Department of Environmental Protection, the copepod count was, on average, 9 organisms per liter of water.

Why don’t we notice the copepods

The copepods that come out of the tap are dead, in almost all cases. It is believed that the prolonged exposure to chlorine, along with the journey through the delivery system, are the causes. The lack of movement contributes to the difficulty in finding the copepods.

All the types of copepods that are found in our water are translucent. This, too, makes it virtually impossible to spot them.

To see what copepods look like, one may inspect a cloth that was placed on an unfiltered faucet. Remove the cloth from the faucet, turn it over into a bowl of water and shake the cloth. The copepods come off the cloth easily. Inspect the water with a strong light. (For best results, use a shallow black bowl with a black cloth placed beneath it.) The copepods appear as dull white specks, similar to sesame seeds in size and shape.


What are Two Purposes of Filters?

Filters for Health Purposes

One type of filter is used for health purposes. Its advertisements state that it removes cysts (such as cryptosporidium and giardia) from the water. All filters of this class are reliable for removing copepods. (Since the filters are designed to remove dangerous organisms from the water— reliability is essential.)

Though these filters are accurate, they are expensive, and usually slow the flow of water. They are typically used for filtration in icemakers, or for providing high quality drinking water.

Filters for removing sediment

Much more common (and economical) is the second type of filter, which is marketed for the purpose of removing sediment or chlorine from the water. This type of filter is typically rated by micron level, varying between one micron and fifty microns. (Filters less than 1 micron are generally of the health type.)

It is important to note that the micron rating of these filters is only nominal. The rating is not necessarily accurate. In general, these filters are not designed to be foolproof, since a consumer who purchases them—not for halachic reasons but for the purpose of removing sediment from the water— does not normally mind if a small amount gets through.

How Could a Filter Rating be Inaccurate?

Question: How could a filter that is rated at, let us say, fifty microns, allow copepods that are larger than fifty microns—to pass through?

Answer: There is a weak point in some filters: the seal that is between the cartridge and the canister that holds it. This seal is what is known as a “passive seal, ” and is the result of the filter pressing against the housing. It is not very secure.

Additionally, with exposure to chlorinated water, the seal softens and allows copepods to come through.

For this reason, one cannot rely on filters that are not tested by halachic authorities.


How do I find a good filter?

There are, nevertheless, filters that are inexpensive and have indeed been tested and found to work reliably. For the most recent list, click on the tab, Recommended Filters.

There is a Jewish company, Glattwater,  that produces filters specifically for kashruth purposes. Their filters are reliable. They can be reached at 718-436-1808.

One final note: The very popular Brita pitcher filter is not effective for copepod removal.

Where Can Filters be Purchased?

Filters can be purchased at plumbing supply houses and hardware stores. Or, contact Glattwater at 718-436-1808.


When Should I Replace the Filter Cartridge

Filter cartridges should be changed when the water flow is noticeably slower. This indicates that the cartridge is clogged. If it is left for too long, it may get damaged and not filter properly.

What Should I Know Before Installing One Filter for the Entire Home?

Whole home (“point of entry”) filters are installed on the water main of the building. It is important to note that it takes a few days’ usage to flush out the copepods from the pipes. These copepods become attached to the bio-film on the inside of the building’s pipes, downstream of the filter. Therefore, water should not be considered clean immediately upon installing a whole home filter. Upon filter installation, one should drain or flush the hot water tank, via the out-take valve at the base of the tank. While it is difficult to completely clean a hot water tank, this will reduce the number of organisms present.

Please note that whole-home filters clog more rapidly than under-the-sink filters, since they filter all the water of the home. It is most practical to install them in conjunction with a backwashing sand filter system, which self-cleans periodically. The combination of a self-cleaning sand filter along with a reliable cartridge type filter has proven to be a very effective and practical way of filtering an entire building. (Backwashing systems are a bit complicated, though, and should be installed only by an experienced installer.)


Is Placing a Cloth Around the Faucet Good Practice?

Placing a cloth around the faucet will reduce the amount of copepods. On a temporary basis, one might want to use a cloth as a filter. However, some copepods will get through, unless the cloth is a tight weave. Additionally, the cloth must be changed or cleaned as soon as it gets brown. Otherwise, the water pressure will push apart the fibers of even a tightly woven cloth, and copepods will get through. Several layers of cloth are more effective than one layer, but the above rules still apply.

Must Hot Water be Filtered?

Hot water need not be filtered if it is not used for cooking or drinking. It is sufficient to install the filter on the cold water supply only.

If one does install a filter for the hot water supply, care should be taken to install a filter cartridge rated for hot water.

Filters that affix to the end of the tap generally require frequent maintenance, due to the small surface area available for filtration. They also produce a weak flow of water.

Another option, which is often more practical, is to install a cold water filter on the cold water intake to the hot water tank. The tank, of course, must be drained before water from the tank is used.


Can I use unfiltered water in a dishwasher?

Dishwashers may be used without any filtration. Even when the dishwasher is fed with infested water, testing has shown that copepods do not remain on the dishes or cutlery.

Can I wash dishes by hand with unfiltered water?

Dishes may be hand washed in unfiltered water if allowed to drip dry without pools of water in them. One should, however, make sure to stack the dishes sideways to allow the water to drip from them. If dishes are left to dry with pools of water in them, rubbing their surfaces with a towel would remove any residual organisms.


Can I wash fruits with unfiltered water?

Research is still being done on washing produce. In the meantime, at least, one should wash produce with filtered water.

Can I drink coffee from a drip coffeemaker?

Even if coffee was prepared with unfiltered water, one may drink it, if it was prepared in a drip coffee machine. Such machines have paper water filters.


Bottled Soda and Other Drinks

Such drinks, even if bottled in New York City, are permitted, since the beverage companies always filter their water.

Icemakers in Refrigerators

The filters in such icemakers are effective in filtering the water ― however, one should verify that a filter is indeed present and functional.