hi sal, this is mike from forsyth. i got 150lbs of rock, sump, etc from u a week or 2 ago. you gave me a mag 18, but i think it may be too powerful. it's been working ok, but i did a 10% water change tonight and now it's messed up. i have to turn the pump down almost all the way for it not to run dry. i think the overflow, pf1200, is draining the same ammount, so it's either that, or the pump. it makes this annoying sound if i have it turned down. i don't know, what should i do???

ok, i put part of a filter sponge behind the overflow to tilt it and let in more water and it working better. i still have the pump closed alot though...

Turning a mag drive pump down is very bad for the pump if you do it much because it heats up badly. A single normal overflow can usually do 600-800 gph. Sounds to me like you need to down grade depending on the size of your tank.

Turning a mag drive pump down is very bad for the pump if you do it much because it heats up badly. A single normal overflow can usually do 600-800 gph. Sounds to me like you need to down grade depending on the size of your tank.

?? Putting a ball valve on the output of a magnetic drive pump and throttling it down doesnt harm it. What do you mean?

1mbrews88- what do you mean it runs dry? If your sump isnt big enough to hold enough volume to runs the pump, then you may have to thriottle it down, but I'm not quite sure what the problem is you're mentioning. Dawgdude may be right about the nsize of the overflow, though, but the pump wouldnt run dry in this case, the tank would overlow.

For example.......I have been using a ball valve on my Mag 9.5 for over a year turned down about half way with no negative effects. It has ran flawlessly without excessive heat that I can detect.

1mbreww88- Sounds like you need a Mag 12 or something equivalent.

Restricting the output of a mag isn't a problem.

How long of a run do you have on the plumbing? If the pump is running and not over flowing the tank then it sounds like the over flow is keeping up. you may just be pumping the water out of the sump and into the pluming. If this is the case just fill the sump a little more and have some salt water to dump in when you turn the pump on. I know if I have my sump at the "full" line with the pump off and then start the pump it gets really close to running the pump dry.

I had a mag drive blow up on me and overheat from what I assume was back pressure on the pump. I was told by Supreme that back pressure on it will cause the pump to heat up excessively and cause failure.

I had a mag drive blow up on me and overheat from what I assume was back pressure on the pump. I was told by Supreme that back pressure on it will cause the pump to heat up excessively and cause failure.
gawd! That is a ridiculous thing for them to tell you. Magnetic drive pumps were created to allow this, thats why they use magnets. The magnets can easily overheat, and expand and mushroom, which seizing the pump, and can make the whole thing garbage, but usually this is due to running dry, or material jamming in the impeller. You want to restict the output, not the input. restricting the input can cause cavitation, and the air in there can cause the impeeler to blow. I have seen thousands of magnetic drive pumps restricted, and have never had a problem with it.

I run my mag 12 restricted for year and a half now using a gate valve after the pump to the return to controll the flow back to the tank.

thanks for the replys guys. it's a 20 somethin gal sump. 2 chambers, one on left is the water coming in from the overflow. protein skimmer sits in as well. water from protein skimmer flows over baffles to the return chamber. water in right side is usually 6-8 inches from bottom. water on right side is 4-6 in. the water from mag 18 goes up 2 ft and t's to the right and left. goes up 2.5 ft to the returns on both sides.

I hear ya but I had two mag 12's in the store I worked at. One was on a ball valve and the other was not. The one on the valve was cut down about half and was GREATLY hotter than the other. That pump started leaking voltage as well......

i did a 10% water change tonight and now it's messed up. i have to turn the pump down almost all the way for it not to run dry.

Did you put in as much water as you took out? What is the water level in the sump with the pump off? I put a piece of masking tape on the tank or sump when I change water so I know to fill it back up to that level. I suspect you may just need more water.

I hear ya but I had two mag 12's in the store I worked at. One was on a ball valve and the other was not. The one on the valve was cut down about half and was GREATLY hotter than the other. That pump started leaking voltage as well......

I've got a Mag 18 with the return tee'd off to a ball valve. If I want to throttle it back, I can open the valve and let some of the water return to the sump. I'm running it fully closed tho' (2 drains and 4 returns).

Right, George I am referring to when there is a large pump mag12+ and it being turned down to much (one return and its at half power) that you can hit problems. I ran a mag 7 on a ball for a while, it did increase the heat in my sump though. Im just trying to say that there are ill affects from it if you arent careful. ie cooking your sump or tank.

when i shut the power off, it's goes to about 3-4" above the running level. i put a little more than was in there. i am worried about overflowing the sump or tank. the sump is: 24"long, 12" width, 16" tall.

And you should. You certainly don't want more water than the sump will hold with the power off. I've a 175 tank and a 55 sump. My sump level probably rises 8 or 9 inches with the power off--it ends up about 3" from the rim.

What is the level in the tank with the pump running? If you've got too much pump for your overflow, the symptom would be that the water level in the tank rises and threatens to (or does) overflow.

I had the same problem(I think) I did a water change one time and turned the ball valve off while I did the change. Dam was it a nightmare to get it balanced back in the right spot, ball valve are pretty troublesome once you move them from the "perfect" spot. Since then I have never touched that darn thing. Too much of a hassle to get it back right, I now do 2 to 3 10 gallon changes a week instead of playing with the BV to do it all at once.

when it's running, the water level in the tank is up to the wooden trim stuff on the top. about 1.5-2" from overflowing. the water level on the skimmer side seems to stay constant. the return pump side keeps slowly getting lower...

That all seems normal. The only place that you'll see the effects of evaporation are in the return section of the sump.

it seems like it's evaporating awful fast..

How much are do you add each day to the tank?

Evap depends on alot. Lights, amount of heat, pumps, ambient room temp. Mainly lighting though. When I added my 250w HQI my evap jumped to 3-4 gallons per day.

pm sent, sorry i've been out sick

I have to top off my 30g sump about every 2 days cause of evap. Might be the same thing your seeing. Dunno tho.

I went through the same thing setting mine up. One thing that helped preventing overflow of the sump was making sure I had a siphon break on the return line. Once I did this I shut off the pump let the water drain to the sump than added water to the sump til it reached the ideal level. I also have an auto top off to keep that level. I live down the road from you when you get back in town I have an extra ATO I can sell you. Pretty good price with the Monroe county discount.