Do I need a backflow preventer to keep basement dry?

[Davej]

I had a plumber over for an unrelated issue (read it here) and I asked if he recommended a backflow preventer in my home. I don't want any basement water issues

He said he only sees backup issues with homes that have a sump pump or a basement bathroom, and I have neither. I do have a drain in the basement for my washing machine however. He indicated that because I had a P trap on my washing machine drain, that I'd be OK. I don't understand how the P trap prevents backups (thought it was for sewer gas), maybe I misunderstood.

I have a decent positive grade to the street. I'm a couple feet higher than the street, not sure if that makes any difference.

 

[Ontario Plumber]

I had a plumber over for an unrelated issue (read it here) and I asked if he recommended a backflow preventer in my home. I don't want any basement water issues

He said he only sees backup issues with homes that have a sump pump or a basement bathroom, and I have neither. I do have a drain in the basement for my washing machine however. He indicated that because I had a P trap on my washing machine drain, that I'd be OK. I don't understand how the P trap prevents backups (thought it was for sewer gas), maybe I misunderstood.

I have a decent positive grade to the street. I'm a couple feet higher than the street, not sure if that makes any difference.

Your plumber sounds imcompetent. A p-trap will not prevent sewer back-ups, it will only protect you from sewer smells. If there is a sewage back up, then it will come up in the lowest drain opening in the home which is usually a floor drain. Every home can benefit from a backwater valve, especially if other homeowners in the are are having them installed.

If a homeowner at the lowest point on a particular street has a backwater valve installed, then any potential back-up would by-pass that home and would come up in the house which was the next highest at grade.

 

[Sponsor]

 

[Reach4]

How is the height of your basement floor compared to other basements in the area? Talk to the neighbors downhill from you. If they have taken measures to keep their basements from accepting sewage, your basement is next. Ask the city if there is any danger of sewer backup in a big rain.

A P trap will not protect you against sewer backups. A simple flapper backflow preventer is not good enough. They leak. Overhead sewers are best. But there are other solutions.

Besides not accepting water from sewers, you need to know when to stop using the sewer.

If you don't have a sump and a pump, you can put one in. Rain water seeping in is much better than sewage. But you would rather have neither.

 

[Smooky]

The term that is most often used when referring to a gravity sewage back-up is a backwater valve.
https://www.google.com/search?q=bac...IB8XJsQS2tIDIDg&ved=0CEUQsAQ&biw=1280&bih=575


There is also something called a sewer popper that allows sewage to back-up into your yard instead of into your house.
https://www.google.com/search?q=bac...QsAQ&biw=1280&bih=575#q=sewer+popper&tbm=isch

 

[hj]

I think your plumber was referring to the fact that the washer's "P" trap is above the floor so it should not be a factor for a backup problem. If you do not have any drain openings in the floor, you probably do not need a backwater valve. As a practical matter, however, unless it is "brand new", a backwater valve will usually only "slow down" the backup, not prevent it, and that's assuming it is in good enough shape to even slow it down.

 

[hboogz]

All - I have a similar inquiry related to the OP's. I do have have an issue with water (and sewage) backing up to the lowest point in my basement (which happens to be a bathroom) I've read about check valve's but reading on how they work, and correct me if i'm wrong, even if the outbound sewer pipe to the city is backed up, it will not prevent water from coming into the basemant bathroom so long as everyone in the house is still flushing the toilet, taking a shower or running the kitchen faucet. As I understand, water retreating from the city side of the sewer pipe would prevent it from coming back into the house, but I'd have to be made aware of the backup quickly otherwise the same results will occur with water/sewage from inside the home.

Because of roots, grease buildup the city side of the house trap gets backed up every so often -- is there really anything that can be done from a plumbing perspective that would prevent water/sewage from coming up through the bathroom drains ?

Thanks,

Harry

 

[hj]

During a "backed up sewer" condition, when the backwater valve is sealed because of the city sewer backup, you CANNOT use any water in the house because that water has nowhere to go except into your basement. Roots and grease buildup are "local" conditions and a backwater valve will do NOTHING to prevent a backup caused by them. If they are the problem, the sewage coming up is water being used in the house and the only way to prevent it is to stop using water.

 

[hboogz]

Exactly. When that condition is triggered it really comes down to me being notified of that backed up drain and snaking/clearing it as soon as possible. There is no way I can prevent people on a the 2nd floor to stop using any water if they are not made unaware of the backed up condition, which means even with a backwater valve until the drain to the city is cleared there is a high/definte possibility that water will back up to the basement bathroom.

Thanks for the confirmation HJ

During a "backed up sewer" condition, when the backwater valve is sealed because of the city sewer backup, you CANNOT use any water in the house because that water has nowhere to go except into your basement.

 

[Reach4]

1. Glentronics, Inc. BWD-HWA Basement Watchdog Water Sensor and Alarm or similar is useful if people can hear the alarm. That particular one is steady -- not pulsing-- but at least it is pretty loud. Condensing humidity can set it off. Disconnect the 9-volt battery to silence it. You could in theory remote the wires.

2. Some people have a sewage pump that pumps into the sewer on the street size of the backwater valve. Amazingly, this is permitted, at least in some places.

3. The flapper-type valves where the sewage presses the flapper open are not reliable, although an ejector pump pumping downstream of the valve can make that workable. The valves that pass sewage until a float closes the valve are much more reliable.

 

[hboogz]

1. Glentronics, Inc. BWD-HWA Basement Watchdog Water Sensor and Alarm or similar is useful if people can hear the alarm. That particular one is steady -- not pulsing-- but at least it is pretty loud. Condensing humidity can set it off. Disconnect the 9-volt battery to silence it. You could in theory remote the wires.

2. Some people have a sewage pump that pumps into the sewer on the street size of the backwater valve. Amazingly, this is permitted, at least in some places.

3. The flapper-type valves where the sewage presses the flapper open are not reliable, although an ejector pump pumping downstream of the valve can make that workable. The valves that pass sewage until a float closes the valve are much more reliable.

Thanks Reach. Do you happen to have a name of what i highlighted in bold so i can look it up? The two plumbing shops closest to me are remarkably unhelpful unless I bring exact names, sku's, sizes, etc.

Dumping sewage out from the house is not allowed here in Queens, NY. Although I've heard of people doing it onto their lawns.

 

[Reach4]

http://www.floodexperts.com/products/flood_prevention_valve.php is a top one, but I expect it is more expensive. I don't know the price of the valve only. It is used in this system: http://www.floodexperts.com/products/flood_control_system.php where the work is all done in the yard and covered with a grass-covered lid when done. It has the advantage of keeping some sewage waiting even if the power goes off for a while. It is usually about $8000 installed.

http://backwatervalve.com/products/fullport-backwater-valve.html is cheaper one I was thinking of. It is particularly popular in Canada.
http://www.backwater-valves.com/ may have the same.

 

[hboogz]

That first product you linked is really interesting. Theoretically, since I do have a sump pit where the house trap is located, if this were to be installed it would replace the cast iron house trap and combined with a 1/2 hp sump pump when a flood condition occurs even with house water still running one could pump water and waste away from the basement until you can clear the stoppage.

 

[Reach4]

While considering options, the gold standard is the overhead sewer. In that, all upstairs sewage is run through a new pipe that goes through the basement wall. Rather than running a new sewer pipe under the main floor, you can have a second new hole go out of the wall at the other end of the basement, through a trench, and join the other sewer pipe before proceeding to the street. Best is when they core drill the holes for the penetrations, and saw the holes for the pits.

The existing sewer is capped. The existing vented sewer pit with grinder pump, or a new vented sewer pit with a grinder pump, pumps effluent up and then down into the gravity sewer. At the same time, if there is a perimeter drain hooked to the sewer it is connected to a separate non-vented sump pit which pumps to a pop-up in the front yard. Figure $10K to $18K depending. I have seen beautiful work with hand digging, where the diggers separated sod, topsoil, and subsoil onto tarps, and put it back very nicely compacting the dirt with sledge hammers. That is not the norm. A backhoe, subsoil on top of your grass, and you are left with a mound of mixed soil that you eventually have the top part removed and replaced with topsoil is more common. With overhead sewers, your upstairs sewers work fine in a power outage. Only your basement loads depend on electricity. Some towns have programs to subsidize this, sometimes to the tune of $5000. Those programs tend to have money only for a while, until the next program.