Hello,
I have a relative with occasional sanitary sewer back up problems through her basment floor drain. The problem is shared by everyone on her block during heavy rain the city storm sewer system overflows into the sanitary system which back up through her basement floor drain.

The city advises not to cap the floor drain due to possible back pressure damaging her tile sewer line.

I've also seen that stand pipes should not be higher than 4 feet to prevent the same possible back pressure damage.

With a overhead sewer system since you block off (cap) the basement lines from the sewer and then pump those lines up and into a higher line haven't you effectivly capped off the drain and turn the other sewer line into a stand pipe that is higher than 4 foot?

Why does that not cause the same back pressure?

Thanks
Steve

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The city advises not to cap the floor drain due to possible back pressure damaging her tile sewer line.

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I have a problem with this. I would demend to know how much backpressure's involved and if the city damages my sewer line why they aren't responsible for the repair.

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I've also seen that stand pipes should not be higher than 4 feet to prevent the same possible back pressure damage.

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What a crock!! Figure the average basement sewer main is only about a footunder the basement floor line that would give you about 5 feet of head pressure.
5' of head pressure = A little over 2 PSI. Two pounds of head pressure? I(f your pipes won't take a two pound load you're in deep doo-doo.

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With a overhead sewer system since you block off (cap) the basement lines from the sewer and then pump those lines up and into a higher line haven't you effectivly capped off the drain and turn the other sewer line into a stand pipe that is higher than 4 foot? Why does that not cause the same back pressure?

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Good thinking Steve! While the basement pit has a check valve so the sewage from the house doesn't drain into it the house has no such protection.
If you have a problem with the city backing up every time you get a heavy rain I woud, for sure, install a back flow preventer/check valve ,(see images)on the house sewer. Good luck, Tom

Agree with Tom 100%: I also think the City is not telling you what they should. First, it is their problem, not yours. You pay them your taxes and in exchange, they maintain City sewers. The check valve is definitively the way to go.

I share both of you guy's disgust with the city but people have tried sewing the city before for this and none have won.

She has a deep sink in the basment so I temporarly rigged (rigged a stand pipe to that level (about 3.5) feet. And set it up to overflow into a tub that has a sump pump in it.

I really want to tell her to just cap off the drain and let the deep sink act at a stand pipe but with my luck the pressure would end up cracking her tile sewer line out to the curb.

I just think that when the sewer backs up into the overhead sewer while it won't flood the basment it still will have just as much pressure in the tile line out to the curb.

Am I wrong in thinking this?

Steve

Let's see if I have this correct.

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The city advises not to cap the floor drain due to possible back pressure damaging her tile sewer line.

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The city is telling you that unless you allow them to flood your basement with sewage your sewer line might what? Explode? Blow the joints apart? I have a lawyer friend here in Sarasota that would just love to get his teeth into a case like this.
Call the building department and demand to know what the PSI of this back pressure will be. It's your sewer that they are threatening to damage unless you allow them to back up sewage in your basement.
Their stand pipe information was a load of crap and I'll bet this is also.
My advice? Install a sewer check valve on the house or a Flood Guard on your floor drain. Let me know how you make out. Good luck, Tom