Backwater Prevention Valves and Halacha


By Rabbi Yair Hoffman for

It is Erev Shabbos.  As you are preparing to go to shul you detect a horrible smell.  It is coming from your basement and you go to check it out.

And then you see it.  Gallons and gallons of raw sewage are coming up from your toilet and who knows where else.   It is a homeowner’s worst nightmare.

But the nightmare does not end.  You call the plumber. He comes and says – there is nothing that can be done.  It is a DEP (Department of Environmental Protection) problem because it is a backup from the main sewer line.

Can this really be true?  The answer is yes, and it just happened to one of my son’s Rebbeim. The DEP did not come until Motzaei Shabbos.  And it usually happens to the last home on the block before a bend.

In South Ozone Park last week, 74 homes were flooded.  Department of Environmental Protection Commissioner Vincent Sapienza had a special town hall session about it and explained that city pumps will continue to operate around the clock to keep it from happening again.

Backed up sewers can cause thousands of dollars in damage.  The damage is to floors, walls, basements, furniture and entire electrical systems. You name it, it can get damaged.  And then there can be the mold and the bacteria and all sorts of other nasty issues that come along with it.  In some cases, it can even seriously threaten the health of the homeowner.


There is a way to prevent the damage, by paying between $600 to $1000 and installing a backwater prevention valve.  But is it permitted according to halacha?  What would be the problem in doing so?  If there is a sewer blockage and it is coming from the street – your backwater prevention valve will cause the neighbor next door to you to have a backup.


We will discuss the guidelines shortly, but first, let’s try to gain a basic understanding of how our sewage system works.

Each block has a city sanitary sewer main which is located in the middle of the street, generally.  It is pitched about a quarter inch every foot so that gravity will carry the sewage water to the treatment center.

Each house has a sewer lateral that feeds into the sewer main in the street.  It is also pitched so that gravity will take it there.

People do not necessarily realize this, but each homeowner is financially responsible for maintaining the house’s sewer lateral.


The Ramah in Choshain Mishpat  388:2 states as follows:

“If he saw damage coming to him, it is permitted to save himself – even though through this – damage will come to another.”

What is the Ramah’s source?  It is a Nemukei Yoseph in Perek HaShutafin in the Talmud Yerushalmi.

There is a caveat, however.  Both according to the SMAH (388:10) and the Vilna Gaon (388:29) It is only permitted to do so – before the damage has happened – before the water has entered into your household.  One it has happened, however, preventing the loss is not permitted – because it is directly causing damage to one’s neighbor.


The case under discussion, however, refers to sewage regarding an outside field.  Our case, however, could be very different.  As mentioned earlier, however, sewage backups can cause serious health hazards that lie beyond mere monetary damage.  Can a sewage backup valve be installed under such circumstances as well?  Does it make a difference if there is a member of the household who is immuno-compromised?

This distinction is made by the Tzitz Eliezer (Vol. XV #70) that there is a difference whether it is merely a monetary issue or if there is a life-threatening danger involved.  True, the Tzitz Eliezer did not deal with sewage back up issues – but the concept remains true.

It would seem to this author that if the neighbor is elderly or if there is an immuno-compromised person next-door – it would be forbidden.  To determine which neighbor is being referred to, one must know which way the pipe is being pitched. It is the neighbor whose sewage pipe is higher than yours – one can ask the DEP which neighbor it is.

It is also a halachic value to prevent your property from damaging your neighbor’s.  To determine how to do this, it is important to know the different causes for sewage backups.

  • Sometimes they can be caused by things being poured into the sewage lines that shouldn’t be poured down there. Concrete, garbage, oils, grease, paper products are just some examples.  Sometimes workers on a construction site just pour it down the sewage pipe – because they don’t live there and don’t really care.
  • They can also be caused by the growing problem of combined pipelines. Although in theory, New York City has two separate sewage systems – one for storm water and one for raw sewage. Some areas combine storm water and raw sewage into the very same pipeline. During many rain storms, the systems are exposed to more volume than they can handle, and the result is a sewage backup situation that allows sewage to spew out into basements.
  • They can also be caused by tree roots that make their way into sewer line cracks and service pipe joints, and can cause extensive damage or blockages as they grow larger.


The halachic repercussions of this may be that we should take precautions recommended by experts in the following areas:

  • Properly dispose of any grease. Cooking oil should be poured into a heat-resistant container and disposed of properly after it cools off, not in the drain. Washing grease down the drain with hot water can potentially cause a sewage backup. As the grease cools off, it can solidify in the main sewer causing the line to constrict and eventually clog.
  • Properly dispose of problematic paper products. Paper towels, disposable (and cloth) diapers, hygienic wipes do not deteriorate quickly and can cause a great deal of trouble in the property owner’s lateral as well as in the city main.
  • Periodically cut tree roots. If you have continuing problems with tree roots in your lateral, you may have to regularly have the roots cut by a professional.
  • Replace your line with new plastic pipe. Plastic pipe will prevent tree roots from entering your line is to replace your line and tap with new plastic pipe.
  • Correct illegal plumbing connections. Do not connect French drains, sump pumps and other flood control systems to your sanitary sewer. It is illegal to do so, and debris and silt will clog your line. Consult a plumber to correct any pre-existing illegal connections.


It is important to note that a backup valve may not make a difference.  To understand which homes it would apply to, go to the following website:


The author can be reached at


  1. this is like if some one is throwing a rock at you, are you allowed to duck even though the fellow behind you might get hit!

    All people should have back flow valves.
    Just like you duck to avoid getting hit by a rock, so too the guy behind him should duck and the guy behind him, etc.

  2. Please note- backwater valves and backflow preventers are very different.

    Backflow preventers are on domestic and sprinkler water mains- in those applications the dep must approve the installation and the preventive must be tested annually by a master plumber. The master plumber files paperwork every year with the dep. if you don’t test them annually with a master plumber you get fines from 1-5k and upwards.

    Backwater valves are check valves that are a gate that allows sewage waste water to flow from a line closer to a city sewer. And if sewage from the city sewer is backed up and pushing back in your house even if you have a backwater valve you can still have a backup in your house. Because let’s say you have a backwater valve and you go to the toilet when there is a backup that the valve is stopping. Your flush in your house can a) push the valve open allowing sewage to come back in your house When the gate is opened or b) will not push the gate and leave your house and will backup into the lowest point- laundry sink or basement toilet etc.

    Consult a good master plumber. There are many who are frum Yiddin- Present company included.

    Yashar koyach Rabbi H! Great job on this article!