Use Many (8) Water Storage Tanks in Lieu of One?

12/23/2024

I work for a local fire department that does plan reviews for fire protection systems. We are reviewing a project that requires 40,000 gallons of stored water. They are proposing using multiple fire water tanks and eight 5,000-gallon tanks.

While NFPA does not restrict the use of multiple tanks, I would like to see fewer tanks than eight. I am more inclined to allow two separate tanks at the most.

However, I wanted to see what others thought and if there was a standard understanding or practice to number or size of tanks to the total needed water demand. Thanks for any help.

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17 Comments

Glenn Berger

12/23/2024 08:07:01 am

The use of 8 tanks is definitely unique. Will need more project information to understand this design solution. Most of my projects will utilize a single tank when required. Double tanks when the water supply is extremely unreliable or when dealing with significant hazards.

Anthony

12/23/2024 08:08:41 am

This is an off choice but I don't think its "wrong" I just wouldn't do it this way.

Cons:
Way more failure points like 8x as many.
Higher costs in maintenance, there will 8x as many alarms and heaters to care about.
higher initial instillation costs with the items above and more concreate for the tank pads.
Could be a lot more heat trace?
More pipe if these are interconnectd

pros:
Might look cool?
Redundancy is always nice.
could be some unknown costs savings?

12/23/2024 08:11:33 am

I don't see any issues with this arrangement. As long as proper arrangement of check valves, float valves, and any other arrangements required to ensure smooth operation are met I would not have issues. I assume this contractor would be using this arrangement to either save money, save time of building a custom tank, or to be able to have the tank arrangement be built in a tight area.

12/23/2024 08:19:34 am

While NFPA does not restrict the use of multiple tanks, I would like to see fewer tanks than eight.

Please remember as a AHJ you may not like something but if it complies with the code(s) then you should approve the plan. This way you do not get into any legal troubles.

J.H.

12/23/2024 08:40:11 am

NFPA 1142:4.1.4 The AHJ shall be permitted to specify how the water supplies required in this document are provided, giving consideration to local conditions and need.

J.H.

12/23/2024 08:20:01 am

Consult with operations, since the tanks are for them to use.
Is the large number to have them distributed throughout a large lot?
It only takes about 4-5 minutes to empty a 5,000 gallon tank, and then the crew has to restage at the next tank for another 5 minutes? No thank you. 9/10 there is no way this is getting approved.

Chad

12/23/2024 08:22:23 am

Maybe you should propose that the operation and maintenance schedule will be adhere to strictly for every single component, and you will be there to ensure that it gets done?

Unless this is some unique arrangement that doesn’t have a lot of floats and other equipment they’re going to quickly do the number that the operations cost is gonna greatly outweigh whatever they are trying to cheap on on, perhaps

Jimmy

12/23/2024 08:50:45 am

8 Tank installed correctly can be within code.
Cost of ITM (inspection testing maintenance) is well X8

If the owner can get the tanks at no cost or reduced cost may be the reason for the request,...... but ITM X8 needs to be addressed.

If allowed, I would have them manifolded.
They would fill equally and drain equally,....

Sounds like the tanks are free to low cost for the request.

J.H.

12/23/2024 09:21:43 am

A manifold situation would be fine, as long as the total refill time is within the maximum 8 hrs per NFPA 22:4.2.1.4.

José Figueroa

12/23/2024 09:49:23 am

It sounds like you have a very unique arrangement, and I appreciate the potential complexities involved. Could you please provide a schematic of the tanks? Specifically, I’m interested to know if they are gravity-fed or above ground, and how they are connected to the fire pump. Are they utilizing principles like Archimedes' or communicating vessels? It would be great to understand whether they are working in parallel or in series, and the configuration, such as one tank positioned above another.

Additionally, while I recognize the engineering challenges involved, could we also explore a comparison of the costs for this arrangement versus using a single suction tank and fire pump as outlined in NFPA 13? Thank you!

Jack G

12/23/2024 10:35:36 am

The only thing i can think of for 8 tanks is that they are being set up inside a heated space? Otherwise the costs to heat and maintain would be astronomical.
Set up would like " building a watch " to get it to work. A lot of " dead "water with 8 tanks so the amount of water in the tanks will be more than the 40 k if that was the amount needed for the duration.
Would a pressure tank ( half in the ground urethane insulation over) no pump ( air compressor ) be more economical?
Hard to say. I installed one of those 50 years ago at a nursing home facility in Dover Delaware.
Still working.
Also had a gc ( new facility ) build a tank in the foundation of a stair tower with a pumproom in the stair. Was a cool set up.
8 tanks are too many in my opinion even though allowed.

Jose Figueroa

12/23/2024 10:48:12 am

Jack, I greatly appreciate your insightful observations about the dead water and heating issues. Your points are extremely helpful. Thank you!

Jesse

12/23/2024 01:22:13 pm

I've was on the AHJ side for a long time. The issue is, the arrangement is not disallowed by code. So, you don;t have a legitimate code reason to reject the submittal.

J.H.

12/23/2024 01:44:29 pm

It is the AHJ's responsibility to reject the submittal if the sum of the parts doesn't meet minimum performance objectives. If they are using tanks, they are already in an alternative water supply situation and they must demonstrate that their arrangement will meet fire department access and water supply requirements, as well as NFPA 22 and NFPA 1142 criteria.

Jon link

12/23/2024 04:36:05 pm

I thonk the reason they're proposing a 5000 gallon tank is due to product availability

Mark Harris

12/29/2024 05:38:59 pm

Had a situation once where owner installed three smaller diameter manifolded tanks sized to meet the requirements. As JL noted it was due to tight spaces and also they were originally planning on a city supply that did not materialize so Jon's note about availability also came into play. Owner did it so no idea on cost. Was in AZ desert near Mexican border so freezing was not an issue. Agree with comments that should be acceptable but may not be the best life of system total cost solution.

Maybe it has changed but NFPA 409 for aircraft hangers used to require water supply from two tanks to still have protection if a tank was out of service. Had unique pump verbage as well. Have also seen pump house between two tanks at an oilseed extraction plant. Eight pumps (four from each tank) to a large header down the center.

Several of the pumps were diesel and first system trip (multiple deluge systems) realized nobody had looked at the combined fresh air intake requirements for the diesel engines and needed to put larger ventilation in. Original ventilation was ok for single pump (and during a single pump flow test) but inadequate when multiple pumps were running.

Ricardo Gonzales Jr

12/30/2024 08:37:10 am

As a former AHJ, does the proposed solution violate code? Feelings can't be defended in court. Unfortunately, I get a lot of AHJs using their feelings instead of facts or the code to justify their rejection of a design. Walking that line can be tough, but always look at it from a "I need to defend this decision from a legal viewpoint". Being on the stand is an extremely stressful situation.

As a few above have stated, what's the situation and cost to use 8 tanks instead of a single 50k gallon tank. It would be interesting to see.

Use Many (8) Water Storage Tanks in Lieu of One?

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