Just a matter of physics

[firefighter26]

Originally posted by NJFFS_A16
WOW....I didn't think it ever got warm enough up there to keep water in a tank....doesn't it freeze like...364 days out of the year??

It does, but the one day it isn't freezing some idiot will light his house on fire..... Best one I seen was christmas morning two years ago.. a sleeping bag on fire in a chiminey... not in the wood stove, in the chiminey, two feet from the top...

[Fire304]

Originally posted by firefighter26

Best one I seen was christmas morning two years ago.. a sleeping bag on fire in a chiminey... not in the wood stove, in the chiminey, two feet from the top...

No way we're letting you go without telling us why there was a sleeping bag in the chimney . Some people...

[firefighter26]

Originally posted by Fire304


No way we're letting you go without telling us why there was a sleeping bag in the chimney . Some people...

I could tell you, but I was thinking of using that story the next time a post that has something to do with "the stangest calls you have been on" comes up... until then I will let your imagination wonder.....

....just like I did when I walked in the the middle of our FR class last thursday and some of the probies wanted to know why there was a picture of me down on one knee, pants down, and a bar of soap in my hand... for the record, it wasn't a bar of soap, it was a plastic spoon with a short piece of string on the end...

You guys miss some really good parties at my station, but that is also for another post.... (note to self, I should have stopped talking to paragraphs ago....)

Anyway, back to the physics problem, everything is sounding great. I will see if I can the specs for the new pump next time I am down at the station (gpm vs psi)... maybe that will make a difference in some of the math.....

[BoneyT]

KEY POINT: Put the inlet at the top of the tank. Ten years down the road your gate valve or ball valve will start to leak from all the use. If you filler is at the top of the tank you will not lose the entire tank through it. (I know we all check the rigs out every day and such, but in the event the leak becomes drastic, it could make a mess out of your apparatus floor.)

[Dalmatian90]

Brain Hurts...must analyze CILFD's info...

Not saying I agree or disagree, I understand you're arguement better now. So now I have to let my mind churn on the physics of the situation for a few days.

So for a 4 inch pipe, you will need to overcome 5.45 pounds of pressure for each 1 foot in rise.

Sorry Devoe, but that's just wrong.

Imagine the size pump a municipality would need to for a water tank, say 50' in diameter. 39,060 pounds of pressure for each foot rise? Nope. 0.434 psi per foot, irregardless of the shape or size of the container.

Fill a 50' tank or 4" pipe 6' high, it's 2.6 psi

[Fire304]

I think the answer you're looking for should be determined by things other than head pressure and lift, since for all practical considerations they are virtually no differences between top of bottom fill.

Top fill will allow you to pump and run better. You fill until the tank overflows, kill the pump, pull the suction and run, no vavles to have to close (and w/o valves no maint of them either).

Bottom fill will allow you to back flood the pump to help the prime, but you'll need to remeber to shut the fill valve once done, otherwise you may end up getting to the scene and find the tank half empty.

Other consideration, an outside 4" fill pipe (to the top) is more likely to freeze on a long haul, so that may argue for an internal pipe where the entire tank would have to freeze first.

I imagine you'd want a quick drain system to dry out the pump in the dead of the winter.

On the other hand, an internal pipe (bottom or top fill) will be subject to corrosion where it penetrates the tank (assuming steel not alum or poly) and will likely be the first place that rots through.

One thing for sure, 4" pipe with an external fill for filling from an engine will fill faster than 2 1/2 or 3".

SO question, how do you keep your trucks from freezing while they are parked in your FD's igloo?