This may sound like a strange question, but here it goes.
Is there a way to downsize a fire water storage tank based on the refill rate supplied by the city?
I know that in Houston there was a company that supplied calculations showing that the refill rate could supply the tank at a refill rate based on the flow test.
Could anyone substantiate this principle?
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5/22/2023 07:41:23 am
This is called a break tank. Ch 14.5 NFPA 22-2018 ed.
5/22/2023 08:28:32 am
I have designed break tanks, but this is a scenario where the city does not have the required flow and the tank is a static tank. In my case it is about 300,000 gallons if i cannot downsize it due to the city supply flow. A break tank is used when the city has enough flow but they want an air gap to insure no back siphonage.
5/22/2023 06:05:00 pm
NFPA 22 standardizes the construction of fire protection water storage tanks for many purposes (including the tank water supply for a fire pump), defining a "break tank" as a tank providing suction to a fire pump whose capacity is less than the fire protection demand.
5/22/2023 08:04:37 am
I've completed a couple over the years, not a break tank specifically, but an allowance to reduce the size of the main water tank based on available refill rates from the local water department.
5/22/2023 08:30:53 am
Is there any place in code where this is allowed? I am not sure if it has been considered in water supplies for fire pumps. Yes the break tank concept is allowed but this is when the supply is sufficient.
5/22/2023 08:07:40 am
I'm pretty familiar with the break tank requirement in Houston. And yes, you can consider the tank refill rate in your calcs. Not just for break tanks, but static supply tanks as well.
5/22/2023 08:32:24 am
Where in code is this allowed? I am more concerned with the static tanks, I have designed break tanks before.
5/22/2023 11:14:26 am
The code does not restrict it. The code allows automatic water supplies and tanks. No where that i know of says you can't combine them.
5/22/2023 08:08:54 am
Yes, we do then possible. It is essentially the same concept as a break tank. We have used this approach several times.
5/22/2023 08:12:27 am
I have done this in remote locations. Need to note, the reason that you have a water tank is that the city utility is unable to provide the required fire flow. Proceed with caution.
5/22/2023 08:34:32 am
Glenn's point is a good one ... Why do you have a tank if the city water is reliable enough to base calculations on? Yes, please proceed with caution especially if you are in an area where development is continuing as "city water refill rates" are subject to change / diminish over time. We don't count on "city power" when we are designing life-critical systems that require backup power as an example.
5/22/2023 08:57:19 am
Yes, refill can be considered for storage tank size, as long as the source is deemed as a Reliable Automatic Refill. This is per NFPA 22.
5/22/2023 09:09:19 am
You're right saying that break tanks are normally used to create a "no connection zone" between city water supply and sprinkler system. The break tank is only used to be refilled by the city water at the rate the pump is taking water from it.
5/22/2023 11:23:31 am
5/22/2023 04:18:38 pm
As others have mentioned, sizing is similar to a break tank.
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