WC sytem - not pulling water

[Peachtree Discus]

I am having a problem with my DIY water change system. Will this design work (attachment) ??

It is basically a pond pump pulling from multiple tanks thru pvc. I am only trying to drain one tank at a time, so all other tank drains are blocked by closed valve. the main lines are all cemented. from the drain in each tank thru the valve and to the main line are not cemented. I was so excited when i finally got it all connected. but , when i turn on the pump, it is not draining anything. If i submerge the pump, it drains at a very good rate.

could it be that the pump not strong enuf? is the lack of cement in sections causing the problem? any idea are appreciated.

[Graham]

If that pump is not a self priming pump then it won't work. Then if it is, the un-cememted joints will leak air in and the prime will be lost.

cement everything,add a valve just before the pump and get a siphon going/fill the pipes with water........ and it will work

[LizStreithorst]

Thank you Graham. I suddenly understand why my self priming pump quits sucking sometimes when I switch it from one water storage container to the other. I have just press fitted, not cemented my fittings.

[Peachtree Discus]

cement, another valve, and a self-priming pump...ok and thx.

actually, the pvc is running between 10-12 tanks, each with a valve at the tank. is that likely to cause a problem with pump establishing a prime?

[Graham]

Very few pumps are self priming, so that means that the pump has to be below the water level to get access to the water. In your pic you show the pipes coming up and over the side of the tank. Unless you start a siphon in those pipes , the pump can't get at the water.

Also with that many tanks the pump once you get it up and running will draw from the closest tank more that the others.

Multiple tank set up are normally done with overflows into a sump and then the pump drawing from there.

[Peachtree Discus]

initially i thought about putting a siphon in-line with each tank exit valve (tank to siphon to valve), but a siphon will be a bottleneck for the flow and will cost me about $80+ (10 @ $8). i already built this mess and would hate to scrap any of it. although, my tank exits are not cemented..so i could use the overflow-sump method, but i am assuming that will be much more than $80

forgive me if i am still not understanding....but if i understand you correctly, if all joint are cemented, are you saying a true self-priming pump WILL get the flow started? is the challenge with this idea simply to find a self-priming pump?

[Graham]

Why not just get a siphon going in the pipes and then the valve can be used to start and stop it.

I have a permenent siphon set up on my drain hose...drop the end in the tank and open the valve... gravity fed siphon...away it goes. In your case you would have a pump that would pull the water through.

Finding a self priming pump is easy...finding one small enough may be the hard part.

http://www.azponds.com/new%20sequence.htm

[Ed13]

Why not just get a siphon going in the pipes and then the valve can be used to start and stop it.

I have a permenent siphon set up on my drain hose...drop the end in the tank and open the valve... gravity fed siphon...away it goes. In your case you would have a pump that would pull the water through.

Finding a self priming pump is easy...finding one small enough may be the hard part.

http://www.azponds.com/new%20sequence.htm

I vote for the simple valve for a permanent prime line although a self pirming pump would be nice! But, $$$ after you look around a $3.00 valve will start looking better and better

These have the baldor motor reputed to be efficient and quiet
http://www.aquaticeco.com/subcategor...-Pumps/pumps/0

or
http://www.aquaticeco.com/subcategor...-Pumps/pumps/1

http://www.aquaticeco.com/subcategor...ming%20pumps/0

Jehmco also has some; product #CWPPA-1/2 has 3,000gph @ 20' @ $186. This is the one I am "eyeing" because I need the height, but call since they have many at great prices
http://www.jehmco.com/html/water_pum...owerheads.html

If you follow Discus KC fishroom build, you'll notice that with an electric gate valve you could potentially automate WC tanks

[Peachtree Discus]

even with the valve b4 the pump...you will lose suction if you drain a tank below the entry point in the tank. so (trumpets playing) what if you lose suction? how do you keep the siphon permenent ?

[Graham]

Simple don't drain the tank below the intake of the pipe.....if you do then you have to fill the pipe back up somehow:mad and that may be a PITA once everything is glued together.

[Ed13]

Simple don't drain the tank below the intake of the pipe.....if you do then you have to fill the pipe back up somehow:mad and that may be a PITA once everything is glued together.

If you put a T and then a valve on the ouside top of the J, instead of a regular elbow you can fill it up there in case in loses the siphon, close the valve and open the draining valve should prime the line again. It should work

[Graham]

Ed the top of that T would have to be able to be shut off or the siphon would be lost. If left open then the pipe becomes an over flow...only what's pumped into the tank would come out.

Basically this whole design is not great using a pump.

G

[Ed13]

Ed the top of that T would have to be able to be shut off or the siphon would be lost. If left open then the pipe becomes an over flow...only what's pumped into the tank would come out.

Basically this whole design is not great using a pump.

G

Exactly, but a sch 40 PVC valve is capable of being air tight? It should work here no? It should be closed untill it's needed to prime the line, then closed again.

[Peachtree Discus]

Basically this whole design is not great using a pump.

its starting to look that way. i've got compression segments so i can disassemble and plugged junctions so i can add on when necessary i may just accept it how it is and try not to drain too far.

thx 1000 wcs for all ur help

[Graham]

Exactly, but a sch 40 PVC valve is capable of being air tight? It should work here no? It should be closed untill it's needed to prime the line, then closed again.

Ed, I was thinking an open T and that would not work, but with a ball valve on it , of course it would work...sorry about that.

Discus maker......create a siphon and don't drain too low but look at re-designing it as an overflow into a sump...it'll work much better

G