# Pressure of water exiting a hole in PVC

• Cmotaval
In summary, the pressure at the start of the PVC pipe is 60psi and the flow will be 5 g/m or equivalent to the volume of water lost. If I am wrong and the volume exceeds what is pump can provide I can change the pump to one with a higher flow. Assuming that no matter what, the pressure at the start of the PVC is 60psi and the flow will 5 g/m or equivalent to the volume of water lost, the pressure of the water exiting the holes is 0.
Cmotaval
TL;DR Summary
Trying to calculate the pressure of water exiting a 1/32" hole in a closed 1" pvc pipe
I have a 1" PVC pipe that is 36" long, closed on one end and hooked up to a pump on the other. The pipe has 10 holes each measuring 1/32" in diameter and I have been trying to use Bernoullis equation to find the pressure of the water exiting those holes. I believe the volume of water that will exit the holes will be 0.16g/min/hole so I wanted to use a pump that has a flow rate of 5 gallons/ min at 60 psi. If I am wrong and the volume exceeds what is pump can provide I can change the pump to one with a higher flow so assuming that no matter what, the pressure at the start of the pvc is 60psi and the flow will 5 g/m or equivalent to the volume of water lost, what is the pressure of the water exiting the holes. I am trying to make a powered sprayer for cleaning a pool filter and was hoping to estimate the pressure so I can choose an appropriate pump and also ensure I do not blow a hole through the cartridge but I am stuck on plugging my numbers into the equation. Any help is appreciated.

Welcome to PF.

Exit pressure is zero/atmospheric, so I think that's not the real question you want answered. And it seems like you are approaching this backwards. The first thing you need to know to get started is what you want. I'll guess you want a certain exit velocity and/or volumetric flow rate, but I don't know. So...?

Welcome to PF.
Since the tube is much bigger than the holes, there will be little pressure lost before the water reaches the holes. The critical thing not mentioned is the length of the hole, which is the tube wall thickness. The available pressure will be lost as the water accelerates and moves along that short hole. The profile of the hole may also be important.

russ_watters
The device is going to be used to clean a pool filter so high volume and high pressure would be perfect but also never easily achievable. For the pressure, the cartridge can take 150psi max and would like to get as close as possible to that pressure. I was hoping to see final formula and then adjust it depending on what pumps I can find to get as close but not exceeding 150psi with the highest amount of volume.

Because the water is in a confined space with a pump going behind it wouldn't the pressure of the water greatly increase as it goes through the hole?

Cmotaval said:
Because the water is in a confined space with a pump going behind it wouldn't the pressure of the water greatly increase as it goes through the hole?
The pressure is provided by the pump. The pressure falls as the velocity of the fluid increases. The pressure at the exit of the hole is atmospheric pressure, but the fluid then has kinetic energy. If the water jet then hits something, so the water slows down, it will apply a force to the thing it hits.

dlgoff and russ_watters
Is this the situation?

#### Attachments

• FILTER CLEANER.jpg
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russ_watters
Let's not go crazy with the math at this stage please. We don't want to scare the OP away. At this point he has some basic conceptual confusions regarding fluid flow; what pressure and velocity are and how they are related. It's why he's not able to tell us what his requirements are. We need to get that cleared up first.

jbriggs444, jrmichler and dlgoff
russ_watters said:
Let's not go crazy with the math at this stage please. We don't want to scare the OP away. At this point he has some basic conceptual confusions regarding fluid flow; what pressure and velocity are and how they are related. It's why he's not able to tell us what his requirements are. We need to get that cleared up first.
I hear you. Loud and clear... I figured I'd just delete the posts for you.

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AZFIREBALL said:
Is this the situation?View attachment 302230
Yes that is pretty much it but with 10 holes but even calculating with 1 hole would be very helpful

erobz said:
I hear you. Loud and clear... I figured I'd just delete the posts for you.
So the reason I can't provide the requirements is that I want to provide the maximum pressure and volume possible. I am trying to make a device to clean a pool cartridge filter and there is not much data as to how much pressure would poke a hole in the membrane and what volume would be most effective for cleaning. The pump will be the main player in the equation and I was hoping to see the final formula so I can play with the equation to evaluate what pump would get me to the volume and pressure numbers I want and what the cost of that pump would be. What I am hoping for as a starting point is to have 5gal/min at 150 psi exit the hole. V2 would ideally be a more powerful pump and I can work my way up to the point of destroying the cartridge and ten scale back but wanted to try to use math to get me to a better starting point. I do realize that some of my terms are incorrect. It has been many years since my college physics days and surprisingly I don't use a lot of this in the OR, or atleast not in this fashion. I am saying pressure but believe In should be saying force or force at the point of impact

Cmotaval said:
So the reason I can't provide the requirements is that I want to provide the maximum pressure and volume possible. I am trying to make a device to clean a pool cartridge filter and there is not much data as to how much pressure would poke a hole in the membrane and what volume would be most effective for cleaning. The pump will be the main player in the equation and I was hoping to see the final formula so I can play with the equation to evaluate what pump would get me to the volume and pressure numbers I want and what the cost of that pump would be. What I am hoping for as a starting point is to have 5gal/min at 150 psi exit the hole. V2 would ideally be a more powerful pump and I can work my way up to the point of destroying the cartridge and ten scale back but wanted to try to use math to get me to a better starting point. I do realize that some of my terms are incorrect. It has been many years since my college physics days and surprisingly I don't use a lot of this in the OR, or atleast not in this fashion. I am saying pressure but believe In should be saying force or force at the point of impact
As we have said, the pressure is zero at the exit. It just is. So, this idea that you can get "150 psi exit the hole" just isn't a thing. But as @Baluncore implied, when this atmospheric pressure jet hits the filter it will apply a force, over a small area, which is like applying a pressure. And you can solve for the flow rate/velocity and force/pressure at the impact if we specify the conditions. So let's use the 50 psi in the manifold and 1/32" hole per the diagram from @AZFIREBALL -- and yes, there's no real difference in calculating for one hole than for 10 (just multiply by 10 after). We can ignore the head loss in the rest of the piping system because we'll assume the velocity will be kept low (generously sized piping) - it'll get us close as a starting point. Yes, you can use Bernoulli's equation to calculate the exit velocity...

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Cmotaval said:
So the reason I can't provide the requirements is that I want to provide the maximum pressure and volume possible. I am trying to make a device to clean a pool cartridge filter and there is not much data as to how much pressure would poke a hole in the membrane and what volume would be most effective for cleaning. The pump will be the main player in the equation and I was hoping to see the final formula so I can play with the equation to evaluate what pump would get me to the volume and pressure numbers I want and what the cost of that pump would be. What I am hoping for as a starting point is to have 5gal/min at 150 psi exit the hole. V2 would ideally be a more powerful pump and I can work my way up to the point of destroying the cartridge and ten scale back but wanted to try to use math to get me to a better starting point. I do realize that some of my terms are incorrect. It has been many years since my college physics days and surprisingly I don't use a lot of this in the OR, or atleast not in this fashion. I am saying pressure but believe In should be saying force or force at the point of impact

I too like to play around with the mathematical model to try and understand the system. I've made a lengthy post that outlines that approach, but I got the feeling it was about to be deleted by the moderator because it was going to "scare you away". So instead of losing all my hard work, I decided to remove it myself.

## 1. What is the equation for calculating the pressure of water exiting a hole in PVC?

The equation for calculating the pressure of water exiting a hole in PVC is P = (ρgh)/A, where P is the pressure, ρ is the density of water, g is the acceleration due to gravity, h is the height of the water column, and A is the area of the hole.

## 2. How does the size of the hole affect the pressure of water exiting a hole in PVC?

The size of the hole does not affect the pressure of water exiting a hole in PVC. The pressure is determined by the height of the water column and the area of the hole, not the size of the hole.

## 3. What factors can affect the pressure of water exiting a hole in PVC?

The pressure of water exiting a hole in PVC can be affected by the height of the water column, the density of the water, and the acceleration due to gravity. It can also be affected by any obstructions or bends in the PVC pipe.

## 4. How does the pressure of water exiting a hole in PVC change with depth?

The pressure of water exiting a hole in PVC increases with depth. This is because the weight of the water column above the hole increases with depth, resulting in a higher pressure at the bottom of the column.

## 5. Can the pressure of water exiting a hole in PVC be greater than atmospheric pressure?

Yes, the pressure of water exiting a hole in PVC can be greater than atmospheric pressure. This is especially true if the water column is very tall or if the hole is located at a lower depth, where the weight of the water column is greater.

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