The Python Challenge

[Fishyfanatic]

My kitchen faucet doesn't have enough water pressure to suck out of the tank either. I have to hook it up to a garden hose outside. You could just lack the suction power in your kitchen.

 

[Fishyfanatic]

BTW, something to remember, you have to measure the tank at the top, not the bottom. Even though the gravel vac opens up at the bottom of the tank, the water still has to climb up and over the ledge of the top of the tank.

 

[asudavew]

Do you have the bottom piece (valve) unscrewed and pulled down all the way?
Mine sucks so hard it sounds like a vacuum cleaner.

Yeah, but I will play with it more this weekend.

I wanted to be able to clean the gravel better....

Do you think it could be due to low water pressure? Maybe I'm just doing something wrong....

I'll try the outside hose tomorrow.

Thanks for the tip!

 

[jim692]

One minor question? Where are you measuring the water pressure at over 80 psi. A plumping "standard" is to keep holdhold water pressure below 50psi, installing a pressure regulator if neccessary. As I understand it, many house hold appliances (say a dish washer) are designed for only 50psi. So usually, the only place you get a pressure measurement above 50psi is an outside hose bibb that connects to the water supply before the pressure regulator. (I learned about some of these things installing an irrigation system a few years back).

I don't know who told you that was standard, but its not.

Standard is the pressure that is required by the MWA (municipal water authority) to supply water to all it's customers while taking into account the age of system, size of water mains, demand rate, zoning classification, height of buildings, time of day, season, and a few other items. This varies greatly.

Municipal water supplies generally range from 30 psi to 175 psi and up. The general supply range for most municipal supplies is usually in the 60 to 125 range. I know of 2 that supply from 200 - 225 psi. I also know several that give you from 25 - 40 psi in some areas.

Most household appliances are designed to a maximum working pressure of 150 psi. You can easily read the plate on your relief valve on the water heater, or the expansion tank, also check the hose on your washing machine, its made for constant pressure not like the garden hose. When you are expected to exceed about 125 psi, you are required to have a pressure reducing valve (PRV). Also a backflow preventor (BFP) on new installations. Most items operate better at 40 to 70 psi WWP (working water pressure) at the item's inlet. This is not the static water pressure (not moving) this is the residual water pressure (flowing) they need.

Get a 200 psi pressure gauge and a few adapters from the hardware store and put the gauge on your laundry sink and elsewhere in the house. You may be surprised.

 

[jim692]

I just bought one, and I can't get it to pump squat out of my tank.... But any idea why the faucet can't start the siphon>?

My kitchen faucet doesn't have enough water pressure to suck out of the tank either. I have to hook it up to a garden hose outside. You could just lack the suction power in your kitchen.

I have a thought on this. Look under the sink at the supply lines going to your faucet. You should see shut off valves for the hot and the cold water. Coming out of these valves is usually a flexible supply line attaching to the faucet. The diameter of these lines may be too small. The lines come in 1/4", 3/8", 1/2" & 5/8" sizes. Generally people buy the least expensive item they can. Cheap = Small in most cases. If you have the 1/4" or 3/8" hose up sizing may solve your problem.

BTW, something to remember, you have to measure the tank at the top, not the bottom. Even though the gravel vac opens up at the bottom of the tank, the water still has to climb up and over the ledge of the top of the tank.

True. I used 50" for the tank height. Some may be taller and some may be shorter. This seemed like a good range.

 

[gzeiger]

A pump's energy requirement does NOT depend on the height to which you are pumping, it depends on the differential pressure against which you must drive flow. Height is one of several factors which affects differential pressure, and if you're only pumping fluid one way then it will be the only factor. In this case where you're pumping the fluid back to its point of origin, there is no differential pressure whatsoever created by the height. The downward flow of water back to the sink draws a suction on the output of your pump which results in an easier discharge flow path and less energy input required. Yes, it takes more energy to pump the tap water uphill to the tank, but it takes less energy to pump the tank water downhill to the sink.

 

[asudavew]

3/8 inch lines for me. But I installed an inline water filter... it lowers the pressure ........

 

[jim692]

3/8 inch lines for me. But I installed an inline water filter... it lowers the pressure ........

Yep, that will restrict the flow and cause a good sized pressure loss.

Anyway to tee the line before the filter and install a valve with hose bibb? Could use a washing machine hose to get into the sink from there.

 

[Fishyfanatic]

GZeiger- My hose lays on the floor so the water has to be pumped upto the top of the tank, down hill to the floor, around the loops of the hose then back up hill to the faucet. I can get water pulled in the Python to the top of the tank but nothing further.

 

[asudavew]

Yep, that will restrict the flow and cause a good sized pressure loss.

Anyway to tee the line before the filter and install a valve with hose bibb? Could use a washing machine hose to get into the sink from there.

Under the sink, the house pipes are 1/2 inch that supply the sink.... I could tee off and add a bib if they make one for 3/8's line.... A trip to Lowe's maybe...

The washing machine is on the opposite side of the wall in the laundry room...
Maybe an adapter on it so I can put two hoses on it..... and then run a hose through the wall and under the sink.. My wife would kill me.. But only if she figured it out!

 

[asudavew]

BTW - Thanks for the help Jim!

For informational purposes only - The water here is so bad I installed an RO system for drinking water and ice. But the water would kill the RO filter in about a month.. So I installed a cheaper inline filter before the R/O and the R/O filter still dies in less than 3 months....

Oh well..I like clear ice!

 

[gzeiger]

Fishyfanatic - you have a water pressure problem, not a hose placement problem. The water flowing downhill to the floor provides exactly as much energy as was required to pump it uphill to the tank.

 

[HooKooDooKu]

I don't know who told you that was standard, but its not.

Standard is the pressure that is required by the MWA (municipal water authority) to supply water to all it's customers while taking into account the age of system, size of water mains, demand rate, zoning classification, height of buildings, time of day, season, and a few other items. This varies greatly.

Municipal water supplies generally range from 30 psi to 175 psi and up. The general supply range for most municipal supplies is usually in the 60 to 125 range. I know of 2 that supply from 200 - 225 psi. I also know several that give you from 25 - 40 psi in some areas.

Most household appliances are designed to a maximum working pressure of 150 psi. You can easily read the plate on your relief valve on the water heater, or the expansion tank, also check the hose on your washing machine, its made for constant pressure not like the garden hose. When you are expected to exceed about 125 psi, you are required to have a pressure reducing valve (PRV). Also a backflow preventor (BFP) on new installations. Most items operate better at 40 to 70 psi WWP (working water pressure) at the item's inlet. This is not the static water pressure (not moving) this is the residual water pressure (flowing) they need.

Get a 200 psi pressure gauge and a few adapters from the hardware store and put the gauge on your laundry sink and elsewhere in the house. You may be surprised.

When I referenced a 50 psi standard (wrong or not) I was being incomplete. I was not talking about what the municipality must provide. I'm talking about what I though most indoor plumbing is designed to withstand. So IF the city was supplying a water pressure significantly above 50 psi, then a pressure regulator was generally installed in the plumbing feeding water to your house.

I know that in my case, pressure BEFORE the regulator is about 75psi, and my pressure regulator is set for 45-50 psi. That way, things like the hoses for the washing machine are only under a constant 50psi load.
Now many times, a piece of plumbing equimpent (like hoses) will have what seems like some rediculously high number (125psi and 150psi being some common numbers I've seen). But these sort of pieces are used so that they can handle momentary pressures that can be much higher (such as occurs when valves are suddenly closed).

So perhaps what it is that I heard was that it is STANDARD to RECOMMEND installing a pressure regulator if your city supplied pressure is significantly above 50psi. I definelty know I've heard that a residential irrigation system definitely recommends a pressure regulator if the city supplied pressure is 80psi or greater.

 

[HooKooDooKu]

A pump's energy requirement does NOT depend on the height to which you are pumping, it depends on the differential pressure against which you must drive flow. Height is one of several factors which affects differential pressure, and if you're only pumping fluid one way then it will be the only factor. In this case where you're pumping the fluid back to its point of origin, there is no differential pressure whatsoever created by the height. The downward flow of water back to the sink draws a suction on the output of your pump which results in an easier discharge flow path and less energy input required. Yes, it takes more energy to pump the tap water uphill to the tank, but it takes less energy to pump the tank water downhill to the sink.

Maybe we are saying the same thing. I'm not sure because I personally am a bit confused as some of the language being used.

However, I do have a basic understanding of fluid dynamics. So I'll try to restate my intensions:

The efficiency of a Python faucet pump WILL depend on the DIFFERENCE in height of the water level of the fish tank (which decreases as the tank is drained) and the height of the faucet pump. It will also depend upon the size of the tubing and the length of the tubing.

First of all, getting the water up and over the rim of the fish tank is negligable, because once you at least get the initial flow in the tube, the energy to lift the water out of the tank and over the rim comes from the water that is falling from the from the rim of the tank back to the water level. This is why once you prime a siphon tube, you don't need a pump to empty the tank. So long at the tube output is kept below the tank water level, the siphon can suck all the water out of the tank without any additional pump.

The next thing to understand is that a colum of water creates water pressure. If you have a closed 10 foot tall tube full of water, at the bottom of that tube, the water pressure will be 4 psi. So if the Python faucet pump is located 10 feet below the level of the tank, then what ever negative pressure the faucet pump is supplying to "PULL" the water out of the tank is going to be supplimented by the 4 psi height difference.

Now if you are on a second floor of your house, and the python goes out the window, down to the ground, and back up inside another window in the bathroom that is on the second floor along with the fish tank, the fact that the water went down to the ground and back up will NOT have an effect on the efficiency of the Python faucet pump because the water going down from the 1st floor is pushing the water backup to the 2nd floor (an upside down siphon). It will be no different than if the python tubing stated inside the house and ran down the hallway rather than going outside (assuming the over all tubing length is the same).

Now if your tank is down stairs, and you attempt to connect the python faucet pump to an upstairs faucet, you again will effect the efficiency of the python pump. In this case, the pump has to "LIFT" the water from the tank to the upstairs sink. The net effect is that the negative pressure from the faucet sink will be reduced by 4psi per every 10 foot of elevation difference between the tank and the faucet pump.

So having a fish tank down stairs and attempting to empty it with a python with the faucet pump upstairs IS GOING TO SIGNIFICANTLY IMPACT THE PYTHON's PUMP EFFECIENCY. Here is why...
If the height differential between the tank and the faucet pump is 10ft, then the act of lifting the water is going to reduce the working pressure of the faucet pump by 4psi. Regardless of what your house water pressure is, because the faucet pump generates a negative pressure, the MAXIMUM size of that negative pressure is... Air Pressure, which is about 14psi at sea level. So even if the Python can generate a perfect vaccum, that vaccum is only going to be 14psi. But if you are lifting the water from the tank level to the faucet pump level by 10 ft, the NET vaccum is only going to be 10psi. And that's assuming the faucet pump could pull a perfect vaccum. I seriously doubt it will.

Beyond that, the ONLY way you can say that the height difference between the tank water level and the python faucet pump doesn't make a difference is if the negative pressure generated by the python faucet pump is so great that the 4psi/10ft doesn't make any significant difference. But When you start talking about a given that the python is creating a negative pressure, the MAXIMUM amount of that negative pressure regardless of what your water pressure is
Because of gravity, air pressure, and siphoning effects, once water enters a tube, changes in the shape the shape and path of the tube

 

[Fishyfanatic]

As I stated in previous posts, I know that I have a water pressure problem. I can re-fill the tanks just fine using the Python and the kitchen faucet (sink sits lower than tank) but I can not drain the tanks into the kitchen sink. I must use a garden hose.

 

[missileman]

Size of pipes, restrictions ect.. do not effect supply pressure, it effects flow or volume of water that can be delivered.
You may or may not have a pressure problem but it does seem you have a flow problem.
Pressure is static.
PS: the test that was done was not effected by his pressure, as stated, it is how much flow you have (gallons per minute)

 

[Fishyfanatic]

I can confirm that my flow is low. lol We would be lucky at 3 gpm.