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Filter priming discussion.

3K views 31 replies 13 participants last post by  PlantedRich 
#1 ·
For those who have been entertained/interested enough to follow the discussion, this is a picture of my filters as they currently are used.

The layout is no doubt hard to follow so let me trace it out and explain a bit about why it is like this.
I move my filters from tank to tank at times and it is often not worth the time to set things in the best way at each house or tank. Some places need short while other need longer. So sometimes it is worth dealing with the small problems of doing what we are calling the "prime" in a less than ideal way. Not by the book but it works better for my overall use.
The 2075 on the left, currently has short tubing which comes straight down and straight up to the tank as the stand is an unusually tall stand. The 2217 on the right, however has a different setup so that I can run from the filter to the reactor and then to the tank.
The 2075 is set pretty well the way the book might advise and there is nothing unusual about the prime on it.
For purposes of discussion, the 2217 is far more interesting as it does have to be dealt with in a different way. To get the canister to fully fill after cleaning, I have to lift the bottom of the reactor to let the air pass on through and up to go out in the tank. The orange strap and flat bottom on the reactor are built to make that easy as this is not a new problem to me. As I have found small details to change to better fit what I do, I have changed some small points on the reactors I build. I do not like to cut the tubing short as that doesn't let it fit at other tanks or houses.
My positon is that the water in the reactor does not let the air in the canister move through and that keeps the canister from filling totally so that the impeller can work. I don't feel that there is any unusual resistance as mentioned because the filter is working before I stop it to clean and work fine after cleaning--if I tilt the reactor to drain the air/water.

Got some pictures of how your filters set so we can look for difference?
 
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#3 ·
I also use a fountain pump with a foot or two of tubing to prime difficult filters. For really hard to start system run the pump until the filter is full and water is coming out of the spray bar and keep the pump running while you plug in the filter.
Other trick: CAREFULLY inhale through the outlet, pulling water through the inlet until a siphon starts.
 
#5 ·
Ha ha what's wrong with doing it the old fashioned way? Or are you afraid to read the next days headlines: 'Tank proud owner poisoned by his/her own aquarium water..'
 
#6 ·
The only time I seem to have to prime mine is when i clean the hoses. Otherwise I open the valve on the output then open the valve on the input and it burps while the siphon fills the canister.
 
#8 · (Edited)
Whoops!! I see the title may not have been clear enough and I didn't say enough about how this post came up. On another post we got way off the subject so to keep from totally bombing that post, I suggested we start a new post. This post was meant to be a follow up to continue the discussion in this post:
http://www.plantedtank.net/forums/9-equipment/1041802-big-issue-new-eheim-could-use-quick-help.html

A recap of what we were into? I had mentioned that I find having water in the output line of canisters, whether from reactors or large droops in the output tubing can cause problems on restart priming. But as there are so often, there are different opinions on whether that is true or not. I had hoped to move the discussion over here.
My drawing as an example was this. I find that when I leave low spots in the output tube where water is left, it gives me trouble when I restart if I don't clear the water out of the output tube by lifting it. I feel having a straight line going up solves this. I also find the reactor used in the way I use it, also prevents reprime for the same reason. When water runs down the intake at the left it will pool in the canister bottom (blue)but stop before filling the can. I feel this is due to the air trapped in the can by the water (red area) in the output line.
that is where there is a difference of opinion as others feel the water is simply pushed out and has no effect.
Been there, done that? Want to throw in your thoughts?
 
#9 ·
What you are saying makes sense. I run my hoses as straight as possible to avoid exactly what you are explaining and it also explains why I have no issue getting my canisters to basically prime themselves simply by opening the valves. Since the hoses are full of water and in essence vacuum locked opening the valves creates enough suction to fill the canister/ I imagine if I had loops in my lines, a reactor, or inline heater, the vacuum process would be nowhere near as efficient and I would have to manually prime my systems.
 
#26 ·
I have an Eheim 2215 with a inline co2 and inline heater both on the outtake of my filter..I also have some sag on the intake hose..but as long as i close the lines after i shut off the filter i have no problems.. no need to be sucking on hoses or any thing..also i notice what helps is having the filter almost or all the way filled up before putting it back to work.. I mean even if on both sides of the hoses where they go up to the connection are empty..once i connect and open vales and turn on i get very little gurgle but it goes away after a few mins and the filter is peachy!!
 
#10 ·
I also have had problems with long runs of tubing (inlet or outlet side) causing problems with starting the siphon.
I have Fluvals, Rena Filstars and Eheims.
They all seem subject to this.
The loop (as shown in red) is the worst, but even if this line is closer to horizontal, not sagging, this still is not great.

Best has been several filters that I set up with pretty much straight vertical tubing. I prefer having some slack in the tubing so I can move the filter as needed to disconnect it when it is time to clean it, or leaving the options open to move it to another tank. However, seeing the much better behavior with the least slack in the lines I think I am going to go ahead and cut the lines shorter where possible.
 
#11 ·
@Diana I had the same line of thought you do but ended up just breaking down and cutting the lines straight. Vinyl tubing is cheap enough I decided it wasnt worth the hassle.
 
#12 ·
Since most of us do have slightly different needs and wants for things, I like to mention small problems of this sort and the solutions I've found as workarounds. For my tubing, I like the Eheim tubing well enough that I don't like to swap it out for what I can find local and easy. That leaves me less inclined to cut it short as I do move my filters pretty often.
Calling it a problem may be overusing the term as it is more of a thing that I need to remember to do than a true problem. Problems are those nasty things where you still have not found a solution. All it takes for me to get the prime right is to lift the tubing so that it doesn't trap the water or with the reactor, I need to rotate it upside down while it clears. When the filter refuses to pump, I suddenly remember it as a problem!
 
#13 ·
Well, another way to handle it is to cut the tubing for a fairly short filter-to-tank set up, then add a mini shelf under the canister if you need to use it on a set up that would call for longer tubing.
I have done something like that, adding a couple of bricks under a can to make it fit.

A filter that is difficult to prime is also more prone to quitting. Usually when I am in a hurry and cannot stop to fix the problem. Better to set it up so these problems do not come up.
This morning while feeding the fish before work I found a filter that had quit. In this case it was a simple fix, and not part of this discussion, except that it was a bit tricky to get it going and keep it going, and sure enough, it was the one that quit.
 
#14 ·
Yes. All because canisters have such terribly weak pumps. People complain about how expensive ada superjets and their iwaki pumps are and buy eheims with pathetic magnetic impellers with only 5% of the torque (I'm one of them). This means we're perpetually forced to rely on trying to get the best pressure before our filters can even do anything close to what they are supposed to. That's why I'm considering switching to a sump.
 
#16 ·
No but a real pump will not be affected by hose angles, length, amount of biomedia, distance of filter to tank etc. etc. They can also expel air more effectively as long as there's just a bit of water and don't gurgle for hours
 
#17 · (Edited)
Well I am wondering how my 75 feet of garden hose with no pump,no impeller,is able to empty the tank to nearly empty and carry the water through several loop's on the floor,up over the arm of a recliner,back down across the kitchen floor,and up into the sink?
All I have to do is suck on the end of the hose till water travel's over the edge of the tank and start's the trip to the kitchen.
As mentioned in the other thread regarding specific filter (eheim 2217) if your sucking on hoses to prime the thing ,your doin it wrong.
I know this to be true cause I did it wrong for a good while.
Nothing wrong with the Eheim 2217's in my view.
Cannot speak to user error other than from my own experiences.
Not everybody can drive a stickshift,does that make a manual transmission faulty?
I think not.
If you have UV sterilizer's,heater's,reactor's,etc pumbed into the filter which can restrict flow, then I can see issues.
 
#18 ·
If you have UV sterilizer's,heater's,reactor's,etc pumbed into the filter which can restrict flow, then I can see issues.
Bingo. That's what having a high tech tank involves and what I expect in a filter. Especially when it's advertised as a bajillion litres per hour. If filters were like cars and advertised their horsepower too then maybe but they don't.
 
#20 ·
No kidding.

It's like buying a car advertised as having a top speed of 180 mph but once you sit inside and put your luggage in the boot it only does 50.

Anyway I didn't mean to sidetrack this already sidetracked discussion[emoji14] I don't have any issues with relying on siphon. (It's not like we really have much choice anyway).
 
#22 ·
Interesting topic - one that I have given some thought to at various times. For priming my pump after servicing, I fill the pump back up with prepared water thru it's intake opening. Once full, I slide it back into place, attach the hoses, open the valve, and if needed hit the prime button a few times. There usually is enough water in the pump head to push the air pockets thru my cerges reactor so that the siphon on the intake side continues.

Now, here is a question that I have wondered for some time (as I don't have the right test equipment) - Several Eheim filters (and I assume others as well?) have a larger intake tube then output tube. Why?
It's not like the filter is going to require more water then it gives up. My best engineering guess would have to center around water weight. This goes back to Roadmaster's discussion as to why he can siphon his tank with a 75' hose. The weight of the water, and the fact that it completely fills/seals the hose allows it to pull tank water "18-24" up and over the edge of the tank. The greater the distance from the top of the tank water to the discharge point of the hose, the greater the water flow (think of draining a 3rd story tank out the window with the end of the hose at grade level - the tank will drain much faster)

So, given that the above is true, would having a 2" pickup tube and hose that is 4' long going to your Eheim 2217 and a 4' long 5/8" hose going back to the tank help filter performance?

The weight of the water in the 2" hose is certainly greater than the weight of the water in a 5/8" hose. The volume of water in a 2" hose is certainly greater than the volume of the water in a 5/8" hose. From a priming standpoint, if your cutoff valves are at your canister filter then I would assume a droop in the discharge hose would be irrelevant given the massive amount of intake water vs the water in the output tube.
 
#25 ·
So, given that the above is true, would having a 2" pickup tube and hose that is 4' long going to your Eheim 2217 and a 4' long 5/8" hose going back to the tank help filter performance?
Not really. The above is not true. The weight or volume of the water does not matter at all. The height of the water column is all that matters.

Since canister filter returns water to the same level from which it picked it up, the entire system is always gravity-neutral. In formal terms it means that static head of this closed system is always exactly zero.

(Note: canister systems with spray bar, i.e. whose return path ends above the water level, do have small static head, but it is insignificant: it is defined by how high the spray bar is located above the water level.)

The weight of the water in the 2" hose is certainly greater than the weight of the water in a 5/8" hose. The volume of water in a 2" hose is certainly greater than the volume of the water in a 5/8" hose.
Yes and yes. But the system is not affected by this. It always remains gravity-neutral regardless of how much water you have on each side.

It is the basic Law of Communicating Vessels: the water level in two vessels is always the same even if you have only 1 ounce of water on one side and 1000000 pounds of water on the other side. The heavier side does not push the lighter side further up. Otherwise, we'd be able to use it to build a simple perpetuum mobile. Claiming that Eheim filter rely on this effect is basically like claiming that every Eheim filter uses a perpetuum mobile built into it.

From a priming standpoint, if your cutoff valves are at your canister filter then I would assume a droop in the discharge hose would be irrelevant given the massive amount of intake water vs the water in the output tube.
The droop in the discharge hose never matters, even if the intake hose is smaller than the return hose.

If the OP observes a problem priming their system it is probably caused by some form of "locking" that occurs inside the reactor (hence the need to tilt/lift the reactor), not by any "droops" in the water path.
 
#23 ·
I'm not sure the larger tubing will help as water pressure depends more on the height of the water column than the diameter of the pipes. It's can get hard to believe at times and I've been through the discussion when working with water lines in a hillside sub-division. Folks often thought they would get different water pressure if we would run their connection to a 4" line rather than run in the other direction to a 2" line. You can change the volume of water available with going to a larger line but the pressure is the same if they are both the same vertical distance down from the source water tank. Since faucets, lines and valves in the house were always less than 2", there was nothing to be gained by tying them to a 4" main. At times we took folks around to prove the point at different houses in the neighborhood. We could talk theory all day and not convince them but actually giving them the experience was always easier.
 
#27 ·
As someone mentioned, this is an old discussion that never seems to get resolved. What I find is that there is always one group who have one or more theories and feel the problem is user error in some way and then there is another group that all have similar problems and don't find the theories work. That seems to be the case again. Several of us do have the same problem which conflicts with the theory of how water works.
I like science and, in general, don't dispute those issues but there are those times when we have done things so often that when we find a difference in theory and real world, I just have to go with real world. I feel I understand siphons and filters pretty well due to the amount of time I've spent with both. I first learned to siphon vinegar out of a wooden barrel into glass jars while customers watched. Believe me, A good drink of vinegar that can't be spit out will make you pay attention!
I also feel quite at ease with canisters. I don't know how long I've worked with them but I currently have eight in service at three different locations and I move and change them often so that I get lots of work with reprimes after cleaning.
I think what I report on the water not coming down to fill the canister is what actually happens. So I get back to the questioning theories and how they might be missing something small that changes the answer. Theory can be considered totally right for a very long time and still not work. Laudible pus, the Narrows bridge, and the twin towers all come to mind. Power company engineers still can't fully agree on how to best ground a powerline!
I don't know what is missing in the question but "something" is wrong at times.
 
#31 ·
As someone mentioned, this is an old discussion that never seems to get resolved.
Just because someone somewhere discusses whether Earth is flat or round does not mean that it "never seems to get resolved".

What I find is that there is always one group who have one or more theories and feel the problem is user error in some way and then there is another group that all have similar problems and don't find the theories work. That seems to be the case again. Several of us do have the same problem which conflicts with the theory of how water works.
There are theories and there are theories. Fundamental physical laws always work precisely and 100% in real world, by definition. 2 plus 2 equals 4 not because it is someone's "theory". 2 plus 2 equals 4 by definition.

Law of Energy Conservation is a fundamental physical law which is always 100% true in real world, by definition. If one makes a physical experiment and discovers that the Law of Energy Conservation does not hold in that experiment, it does not mean that Law of Energy Conservation is somehow "just an approximate theory" that does not agree with "real world". It simply means that one screwed up one's measurements.

The same applies to physical laws in this specific case. There's no "theoretical" imprecisions of any kind in the behavior of communicating vessels. The "real world" always behaves precisely as the corresponding "theory" predicts. There's no way around it. Every time you see a different behavior - it does not mean that "real world" disagrees with that "theory". It simply means that you screwed something up in your experiment.

I like science and, in general, don't dispute those issues but there are those times when we have done things so often that when we find a difference in theory and real world, I just have to go with real world.
There's no competition between the "theory" and "real world" in this case, so there's no need to choose between one or another. It is just a matter of finding the mistake that acts as the proverbial spanner in the works.
 
#28 ·
If you are DIY-ing some sort of reactor/UV light chamber/extra media chamber, made from PVC tubing/fittings, off your main aquarium canister's output line, wouldn't it be best to plan ahead and put in little fittings/ball valves in all the high spots where air could be trapped, to bleed it from the system so this isn't a major hassle?
 
#29 ·
I don't think of the physical tubing or filter as a problem as I know what to do when it happens. I lift the tubing or reactor and let the air out and the water comes in to fully fill the canister. No big thing!
The question came about when I mentioned it as something that we might need to be aware of if we are having trouble with getting the filter to pump after we do the cleaning. When I made the comment about droops in my line making the canister not fill right, others chimed in with technical reasons why it was not possible.
So that leaves me pretty sure of what I see on my filters and tubing and the other side seeing no way that it can do that. There is a disconnect of sorts between what we might expect from a theoretical view and what I see when I clean filters. No problem to solve as I just lift the drooping spots and it clears. If it is on the filter with the reactor, I have the reactor loose at the bottom and lift it to clear the line. Some of us have it when we have drooping tubing, others have the question when they have reactors. But the theory is that it can't happen.
So the discussion is not how to solve the problem but why is there a difference in the theory and what we find happening. If it were a new question it might not get much interest at all but then it is something that has been discussed several times and several places when people have had trouble getting their filters to pump after cleaning them. I generally feel most agree that the problem is that there is air trapped in and around where the impeller sets and since the impeller is not designed to pump air, only water, it fails.
It seems to happen but then that is in conflict with what theory says can't happen!
 
#30 ·
...and then there is another group that all have similar problems and don't find the theories work...
raises hand

Thats me!

Here is another issue that I was not aware of, but seems to be happening now that I monitor my own canisters.
If the intake is restricted (dirty sponge over the intake) then the pump keeps on removing water out of the can, causing... well, not so much as a partial vacuum, but at least a very slight lowering of pressure in there.
This can cause an air leak on the intake side of the system if there is even the slightest compromise in the O-rings. This builds up air in the can until it does not work any more.
Since I was made aware of this issue I have found the following:
~Filters that no longer siphon can be cleaned, and the intake sponge must also be cleaned. The intake sponge ought to be as coarse as possible so it does not trap the finer particles. Finer particles go through the intake sponge and get trapped by the media inside the filter.
~Filters that appear to have an air leak, meaning air is getting in to the can might not actually have an air leak- some of the trapped gases are leaving the water in the 'partial vacuum' that is inside the filter can. I have lubed and changed O-rings and gaskets, and not solved the 'air in the can' problem. But keep the intake clear and the problem goes away.

Filters with a clear passage, and it is kept clean seem to be able to overcome several difficulties. But when any part of the system is compromised other issues crop up and the equipment can fail.

However....

Fluval 'starter/siphon' whatevers are garbage. Those plungers do nothing except blow the end off the intake. I have about a dozen from the 204 to the 405, and none of them work. Gotta start the siphon some other way.

Rena Filstars with the removable cap and funnel work when everything is right. Another way that I can get these to start, if there is a partial siphon but it just won't run is to remove the outlet tube from the tank and lower it, holding it over a bucket until the water flows. Then lift it back up and into the tank. It usually burps and bubbles, suggesting to me there was air trapped in the system somewhere.
 
#32 ·
I find most of the canisters we use all have some different level of the same problem of trapped air. And it does come about for what seems to be different reasons, even though science says the siphon should fill the can.
Something that I found in the Eheim directions seems to indicate that they are aware of the possibility. The way to setup the tubing is left pretty vague and very little is said in the directions I read. But this is a note from one of the online manuals for the 2215/2217 filters.



Since it mentions airlocks as a possible problem, I would think it indicates they are aware and thinking they might occur even though theory says the canister should fill totally.

Just another of those small things that can make our hobby easier if we keep aware of the possibilities?
 
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