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City of Ann Arbor SSWWEP - Citizens Advisory Committee Coordination — City of Ann Arbor

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SIPHON BACK UP SYSTEM, lets try this again

Posted by Frank Burdick on 15 Feb, 2014
Category: No category

Q. The domestic water siphon "back up" system for sump pumps is more reliable than a 12 volt battery back-up system.  The City's website states the following: (This system)"Uses about 2 gallons of pressurized fresh water to pump out 1 gallon of sump water. Water usage will show up on the water bill."  What would the estimated flow rate be, to the Storm Sewer system, during PEAK FLOW periods, for one Target Neighborhood, such as Orchard Hills, if ALL of the  ("99% of homes in this Target Area are equipped with FDDs per OHM") WERE equipped with water siphon back up systems?  What would be impact to the Peak Flow rates to the Storm Sewer systems to the Morehead and Churchill areas?  Can the City justify the "sustainability" impact of using this quantity of domestic water for the purposes of satisfying the goals of the FDD program? 
 
A. The 2 to 1 computation is a relatively easy computation to make, but that condition only occurs in the rare condition of the failure of the sump pump. I can think of two primary failure modes of a sump pump: 1) when the pump itself burns out, and 2) power failure. Presumably in condition 1 - sump pump failure, the impacts on the storm system would be negligible, as it is not likely that very many would occur simultaneously. In condition 2 - power failure, the impact on the storm system would depend on the extent and frequency of power failures. It is this piece that is not so easy to quantify with our current information in hand. Perhaps the survey might help us understand this piece, by examining the answers to the questions about water in basement. I would suggest that we wait for those results before commenting further.

From Frank Burdick:

The purpose of this question is to help us make a recommendation for back up systems.
This response is incomplete.  It should have been allowed to remain open until after the survey results were addressed.  In addition, our "engineer" on the project should provide a calculated solution the hypothetical scenario noted in the question.  As Hupy said... engineers design system to be redundant and to the worst case flows... etc... .  

Should this SSWWE CAC recommend water siphon back ups on ALL pumps?  If so... well..... please re-read the question and provide a complete answer.   Please assume a 5 hour storm event.  Thank you.

Comments

Joe Conen on 15 Feb, 2014:

I believe that the water back up system requires periodic testing by a licensed plumber and inspection by the city. I will post a question to see if we can get  required frequency and an estimate of the costs for this.
Joe
Maybe we can recommend the siphon backup where it is impractical to co-locate a sump with a floor drain.

Peter Houk on 15 Feb, 2014:

Joe--good questions.  I would like to know about that too.

Patricia Marten on 16 Feb, 2014:

At least one of the 'pilot' homes, in the Dicken school area, got a water back up.  Did they all?  The city should be able to tell us this.  And also could give us the usage for the last 10+ years.

Lori Byron on 12 Mar, 2014:

[CITY]

A: According to the 2001 SSO Report, water-powered backup pumps were installed on the 11 pilot homes .  We’re unclear on the usage question.

Patricia Marten on 12 Mar, 2014:

It would be nice to find out more info on these systems.  
1. Do they require maintenance and/or periodic testing (as mentioned by one CAC member)?
2. What do the pilot homes' water bills (since their have a separate meter) register for usage?
3. Do we have any idea how other homes have water back-up systems?
Thanks

Jim Osborn on 13 Mar, 2014:

Any pump should be tested. It is quite easy to do. And no, you do not need to be a licensed plumber. I test mine, as well as my parent's home in southern California whenever I visit.

to test a normal sump pump:

1) dump in a bucket of water, see if pump turns on and pumps it out.

to test a water backup pump:
1) unplug (or turn off breaker) to main sump pump.
2) dump in a bucket of water, see if the water-powered pump pumps it out.
3) restore the power to main sump by plugging it back in or turning breaker back on.
4) dump in a second bucket and see if the main sump turns on and pumps it out (this tests both pumps and ensures that you restored the power to the main pump.
Of course it doesn't hurt to evaluate the on and off level and adjust if needed and to clean out any debris from the pit, and if there is a careen, is it clear?
But now we are venturing into maintenance, not just testing to see if it works.

A separate water meter is not needed. If it is just an emergency back up pump, then this will not be used that often and if used, the city could have a policy of charging the home's average rate and not a high rate for that month. They said that they will do this for me after a burst pipe used a lot of water.

An alternative is to have a sub-flow meter on the inlet to the b\u pump, and subtract its reading from the main meter. This could reduce the plumbing installation costs. Apartments owners often use this type of low cost meter to charge each unit separately, as the landlord pays just one bill to the water company or city.  

Jim Osborn on 13 Mar, 2014:

"Should this SSWWE CAC recommend water siphon back ups on ALL pumps?  If so... well..... please re-read the question and provide a complete answer.   Please assume a 5 hour storm event."

Yes. Water siphon back ups for all FDD at all homes.

And enough room in any sump pit for both pumps and a third (or a single larger pump) if a home is discovered to produce a lot of water.

The sump pumps should be a quiet operating model, and not the cheapest one found at a big box store.

Joe Conen on 14 Mar, 2014:

Jim, let me clarify the periodic testing requirement I mentioned. I do not believe there is any requirement to test the pump. I do believe a "backflow preventer" is required as part of the installation of the water powered backup pump. This is to protect the city water supply, I think.
I was informed that the city requires periodic testing of this backflow preventer. The implication was that a licensed plumber is required to do this. When I asked a plumbing company, they estimated this testing would cost about $125 if no repair was needed.
Joe
By the way, I posted a question on this topic several weeks ago; it has not been answered yet.

Jim Osborn on 14 Mar, 2014:

Thanks Joe, for your clarification. I misunderstood it. So, this is testing of a back-flow preventer for the water supply, needed in case the water pressure were to be temporally lost, since this supply will be in a pit with sump water.
1) is there a code requirement?
2) If not, should there be?
3) Who or how should this testing, if desired, be performed.
4) $125 seems very high, could this be a city performed inspection, at no cost to the homeowner, with city personnel?
It seems very wrong to require a system, then the testing of it, and then to charge a large amount to the homeowner. If I were such a homeowner, I'd feel like a victim
The testing should not be that difficult, and any repair most likely is a removal and replacement.

Joe Conen on 14 Mar, 2014:

So I got parts of this information at various times over a long period of time, and I do not consider myself an expert. The $125 estimate ($126, I think was the exact estimate) was a verbal "off the cuff" response during a recent discussion I was having with a plumbing company. I would like to see a better (higher confidence) number, but this estimate seem in line, since the testing would involve a plumber coming to your home.
The requirement for testing and for city inspection after testing was described to me several years ago as a requirement that had not been enforced in the past, but people were suddenly (at that time) receiving notices from the city to enforce this.  I was also told that the city charges the homeowner for the inspection (on top of the plumber bill they already got).  It would be good to separate myth from reality here, and that is why I posted a question last month.  I do not know whether this is local or state requirement.
By the way, the plumber informed me that repair or replacement of the backflow preventer was expensive, but did not say how much.
We need the facts to effectively consider this detail.
Joe

Greg Marker on 14 Mar, 2014:

Joe and Jim,
I have some data that can narrow down some of the unknowns.  I added them in red below.

1) is there a code requirement? – It is my understanding that the AWWA cross connection requirements are referenced by the MDEQ and the City has agreed to follow them as a public water service provider.  The cross contamination guide references a licensed plumber testing and verifying an RPZ valve at no more than five years of use, annually in locations with high risk (like chemical pools that have a water source to them).
2) If not, should there be?
3) Who or how should this testing, if desired, be performed. I believe that a licensed plumber tests the operation of the two valves and the dump port to ensure they activate within the specified pressure differentials on either side of the valves.

4) $125 seems very high, could this be a city performed inspection, at no cost to the homeowner, with city personnel?  It is my experience that the usual cost for this is $80 when the RPZ is brought to a plumber, In the case of water siphons, the cost of the service call or any replacement parts would be additional to this.  It has been my experience that the needle valves fail in these occasionally, usually at a cost of $10 or less to repair.

Greg

Jim Osborn on 14 Mar, 2014:

Thanks Greg for your input.

If I were to call a tow truck to tow my vehicle, it would cost a lot, over $100. But, I'm a member of AAA and they have a contract that pays the tow trucks a lot less, under $40 and perhaps even less than that.  I mention this because the city could get a firm to do this at a much reduced rate.

Or, they could perform the inspections themselves, at no cost to the homeowner, and at a low cost to the city water dept.

Michelle Lovasz on 15 Mar, 2014:

Really good ideas Jim, thanks.