Can an external pump be mounted above the wet/dry?

[robshippy]

I am in the process of replacing an old Rio submersible pump with an
external Iwaki MD 70RLT pump. (one of Iwaki's pressure rated pumps
in case I need to restrict the flow with a flow valve). Could someone
please tell me... Am I allowed to mount the Iwaki pump on a shelf just
above the wet/dry? Or does the pump need to sit on the same surface as
the wet/dry. In other words, I really didn't want to cut a hole in the side of
the wet/dry. Additionally there isn't a whole lot of extra room for the
pump to sit next to the wet/dry even if I did cut a hole.

I was hoping that it would be okay to mount the pump on a shelf just
above the wet/dry. I was going to connect the intake of the pump to pvc
pipe that drops down into the water in the wet/dry. The distance from the
water line in the wet/dry to the pump (on the shelf above) would be
somewhere around 18 to 22 inches.

Will it work?
Thank you,
-Rob

[Rick O]

Rob,

Am I allowed to mount the Iwaki pump on a shelf just
above the wet/dry?

Yes you are allowed....but it may not work . Most pumps won't pump air, so they need to be primed. This means that water needs to already be in the pump for it to start pumping. You can test your pump to see if it will self prime before re-configuring your plumbing.

HTH. Rick

You may be abvle to make it work by priming it as Rick mentioned but I don't think it will restart after power down situations. These pumps arent self priming so they are mounted at water level so the impellor chamber is flooded

------------------
I thought I was me, but we were wrong
email: geeflipr@internetcds.com

[snazlord]

can i use an external pump without a drilled tank? In other words, could i run the intake line up and over the edge of the sump?

On the aqua-medic website, the directions for their ocean runner pumps say

"The pump may be set up sumberged or dry. It is however not self-priming and, if set up dry, it has to be placed below the water level."

It then has a diagram of the pump set up on the floor next to a sump/tank, with the intake going up and over the side - Not thru a bulkhead!

I wasn't aware that this would work, although I suppose it would be like a U tube in an overflow in the sense that if the power went out the siphon shouldn't break, allowing a restart.

Has anyone actually used this setup?

[sfletch3]

You might inquire with the manufacture to insure the pump can develop enough suction head to operate without cavitations at 18" to 22". If it will, then another alternative to preventing the restart problem would be to install a check valve at the suction intake in the sump. If power were to fail, the check valve would prevent water in the suction line from draining back into the sump. When power is restored the water in the suction line keeps the pump primed.

[laddy00]

Most pumps we use are for pushing water not pulling it could cause premature failure or cavitation like sfletch3 stated. To be safe check with the manufacturer. If you use a check valve place it after the pump. If it is before you will increase the low pressure behind the pump and can pull air into your return line through your connections even when cemented.

[tdwyatt]

Originally posted by snazlord
...the directions for their ocean runner pumps say: "The pump may be set up sumberged or dry. It is however not self-priming and, if set up dry, it has to be placed below the water level."...

If the impeller chamber isn't flodded without any power, including when the check valve is included inline (don't depend on the check valves to work...), then the pump will not work. They will NOT pump air, and will not dependably suction the height up and over a tank wall, even if it is only a few inches.

Best to redo your sump and have a wet run of pipe through to the impeller chamber.

HTH

[snazlord]

Originally posted by tdwyatt
Best to redo your sump and have a wet run of pipe through to the impeller chamber.

HTH

If I understand you correctly, the only way to do this is to have a drilled sump.

But, for the sake of argument, if you were initially able to prime the pipe (i.e. completely fill it with water) up a few inches over the edge of the sump, then down to the pump, then shouldn't it "hold" the water during a power outage just like the water in a U-tube (which also goes over the edge of the tank)?

[snazlord]

after futher thought, and in reply to myself, i think that my last scenario would only work if the pump outflow also had water in it during a power outage, so that the impeller chamber remained full of water.

This might work if you only had a check valve on the outflow pipe but not a siphon-break drilled into the pipe (which by letting in air during an outage would successfully stop the display from overflowing back into the sump, but would at the same time break the siphon between the pump and the over-the-edge pipe to the sump)

..if you get what i mean...

[tdwyatt]

Heh!!!

Good answer!
Even with a check valve, the possibility exists that some sediment or abiotic precipitation of Ca on the check valve will keep it from shutting completely, allowing the water to drain back into the sump until the water siphon breaks altogether. To be foolproof, you would need to drill the sump at the lowest point possible and have the line drain directly to the pump impeller chamber. Don't want to drill the sump? Replace it with a rubbermaid container and put a bulkhead in it...

[snazlord]

i've thought about that, but haven't figured out how to put in baffles for a bubble-trap since the rubber-maids aren't exactly square. Don't you have bubble problems, especially if your skimmer runs out of/into your sump?

[tdwyatt]

Nope, that particular sump in the pic handles about 3500 gph AND has one of Andy Dias's MR2 skimmers in it. To build your baffles, keep in mind that they just need to slow most of the water down and do not need to be water tight. I have constructed a 2x4 box around the container to keep it from bowing out excessively, then constructed vertical walls of acrylic to creat runs that give basically 3 times the length of the container from where the returns dump the water to the opening for the pump.

I placed the Mag 12 (dedicated to skimmer use only) on the up-current side of the skimmer so that the exhaust from the skimmer isn't picked up and reskimmed again. By the time the water gets to the pump for the return, it is relatively bubble free. I do use an over and under baffle just prior to the sump to make sure that it makes one last gebubble trip prior to intake by the Dolphin at the end of the sump. The baffles are, for sure, not water tight, but they do what is needed to make this arrangement work.

HTH