Plumbing question

[Myka]

Originally Posted by sphelps

Sorry but you folks are incorrect. First off more pressure doesn't mean more flow, yes the smaller the pipe the more pressure, head pressure so less flow. Actual head pressure is only a function of density, height and gravity not cross sectional area. You also however have losses from pipe design which includes pipe friction from pipe diameter, finish, flow regime, and the number and types of fittings used. Bottom line is the bigger the pipe the better as fiction reduces with larger pipe sizes, however you will max out the benefit depending on flow rate.

I didn't say more pressure increases flow! Where do you see that? A person will get less gph, but more psi at the end of a 1" pipe than using the same pump on a 3" pipe.

This is the same principle for powerheads which an impeller produces less gph, but more pressure, and a propeller produces more gph, but less pressure. How a MJ1200 with 198 gph will blow the flesh off certain corals placed 4" away where a Koralia 1 with 800 gph won't.

[BC564]

I agree with you.....but that is something different ......your putting the same volume through a smaller pipe....which increases pressure...

I thought we were just talking about head pressure ???????

[Reefer Rob]

[quote=Myka;400466]A person will get less gph, but more psi at the end of a 1" pipe than using the same pump on a 3" pipe.
QUOTE]

Put a pressure gauge at the end of each pipe and it will be the same.

[banditpowdercoat]

I can see where I got screwed up. The volume increases in the larger pipe. and pump only displaces a certian amount of water. Ya the larger pipe will not add anything to head pressure. Like the difference in a drain. Take a 40g tank, and a 140g tank, both of same height. Drill a 1" hole and install a bulkhead in it. Think of the tank as the larger pipe. more volume, right. Which would have more pressure at the 1" bulkhead? Neither

I was kinda thinking backwards in my previous post. It doesnt matter how large the pipe is, the pump is only pushing put it's amount of water, regardless. When working on gravity, water falling down a pipe, then the PSI gains as the pipe narrows due to the velocity of the water, not just head pressure.. Principal behind Hydraulic strip mining

[Myka]

Originally Posted by Reefer Rob

Put a pressure gauge at the end of each pipe and it will be the same.

No it won't be. The pump will be restricted by the decreased flow out of the end of the pipe...the same reason fittings on a pipe decrease pressure. Now, if you close the end of the pipe you would be right.

[Reefer Rob]

Originally Posted by Myka

No it won't be. The pump will be restricted by the decreased flow out of the end of the pipe...the same reason fittings on a pipe decrease pressure. Now, if you close the end of the pipe you would be right.

I think you're getting confused. Decreasing the pipe diameter will increase back pressure at the pump, but I don't think you can use it to increase PSI at the outlet that way. Think of the applications for that kind of technology Perhaps you're thinking of velocity? I'm not sure what that has to do with head pressure though, which is influenced by gravity, not a pump.

[Myka]

Originally Posted by Reefer Rob

I think you're getting confused. Decreasing the pipe diameter will increase back pressure at the pump, but I don't think you can use it to increase PSI at the outlet that way. Think of the applications for that kind of technology Perhaps you're thinking of velocity? I'm not sure what that has to do with head pressure though, which is influenced by gravity, not a pump.

Maybe I'm not being clear about what I mean, or maybe you're wrong.

We use say 1200 psi to go through a 5/8" hose then through a 1/8" fitting on the end (we use this on Hydro-Vac trucks to cut the ground), and voila! It will cut your toes off. If we use 1200 psi pumped through a 3" hose (which you would never be able to hang onto, and you'd need a muuuuuuuch bigger pump to get 1200 psi out the end of a 3" hose), and you wouldn't hurt your toes with it.

So...slap your fancy words (pressure, head pressure, velocity, psi, flow, whateeeever) on that equation, and tell me what the heck you mean that I am wrong.

[golf nut]

Originally Posted by Myka

Maybe I'm not being clear about what I mean, or maybe you're wrong.

We use say 1200 psi to go through a 5/8" hose then through a 1/8" fitting on the end (we use this on Hydro-Vac trucks to cut the ground), and voila! It will cut your toes off. If we use 1200 psi pumped through a 3" hose (which you would never be able to hang onto, and you'd need a muuuuuuuch bigger pump to get 1200 psi out the end of a 3" hose), and you wouldn't hurt your toes with it.

So...slap your fancy words (pressure, head pressure, velocity, psi, flow, whateeeever) on that equation, and tell me what the heck you mean that I am wrong.

I think the pump comes into play here, I agree with what you can do to cut my toes off (God forbid) but you are using a positive displacement pump that doesn't know the meaning of the word backpressure, a typical aquarium pump doesn't come close to 3 psi and simply doesn't do what a hydraulic pump is capable of, in effect you are both right.

[sphelps]

Originally Posted by Myka

Maybe I'm not being clear about what I mean, or maybe you're wrong.

We use say 1200 psi to go through a 5/8" hose then through a 1/8" fitting on the end (we use this on Hydro-Vac trucks to cut the ground), and voila! It will cut your toes off. If we use 1200 psi pumped through a 3" hose (which you would never be able to hang onto, and you'd need a muuuuuuuch bigger pump to get 1200 psi out the end of a 3" hose), and you wouldn't hurt your toes with it.

So...slap your fancy words (pressure, head pressure, velocity, psi, flow, whateeeever) on that equation, and tell me what the heck you mean that I am wrong.

Adding a nozzle will increase dynamic pressure within the nozzle and increase the head pressure on the pump, but this will result in less flow on a centrifugal pump. In addition as stated positive displacement pumps are not effected by head pressure, they pump the same amount of fluid no matter what. Of course they do have a maximum operating pressure before something blows up which is why such pumps will have a release valve for safety.

You can't relate such systems to aquariums, we use centrifugal style pumps where head pressure is relevant, I'm actually pretty confused on what you argument is at this point

[banditpowdercoat]

Originally Posted by Myka

Maybe I'm not being clear about what I mean, or maybe you're wrong.

We use say 1200 psi to go through a 5/8" hose then through a 1/8" fitting on the end (we use this on Hydro-Vac trucks to cut the ground), and voila! It will cut your toes off. If we use 1200 psi pumped through a 3" hose (which you would never be able to hang onto, and you'd need a muuuuuuuch bigger pump to get 1200 psi out the end of a 3" hose), and you wouldn't hurt your toes with it.

So...slap your fancy words (pressure, head pressure, velocity, psi, flow, whateeeever) on that equation, and tell me what the heck you mean that I am wrong.

But were not changing the pump. What would your 1200PSI pump out out with a open 4" hose, No nozzle. I guarantee you it wont be 1200PSI. But it still woould take your toes and whole feet off if it was exiting the hose at 1200PSI

I'm not acctually sure where this is going anymore, but head pressure is irrelavent of the volume, its height. Thats the main reason why our tank glass gets thicker the higher the tank gets. Higher water, more pressure. Regardless of vessel size. Just like pressure in the Ocean at 15ft below, is the same as in a pool at 15' below. Head pressure has nothing to do with flow or anything. Its just the weight of a column of water.