Pump won't restart, nor will new one

[John Zillmer]

I have a Iwaki MD55RLT in the basement that pumps fresh SW up to my 90g reef when I do a water change. It is triggered by a float switch in the sump so that as I siphon water out, it gets replaced. I do this with the return pump running (so not to drop water level in the tank below the higher corals), so it pumps about a gallon, then stops pumping (during which time the hose to the basement backflows into the SW reservoir, since I never saw a need for a backflow valve) until the switch is triggered, then pumps another gallon or two, and so on.

Anyway, years ago I'd bought a used Iwaki pump for this setup and it was unreliable about restarting about halfway through a water change -- I'd have to manually raise and lower the float switch 4-5 times before the pump would restart. I thought the used pump I'd bought was glitchy and I simple dealt with it.

Recently I installed a brand new pump (same model), and I experience the same failure to restart, after the pump has run about 6 or 8 fill cycles. And same as the old pump, the new pump does restart after I manually raise and lower the float (that is, after I apply and cut power to the pump a couple times).

Any idea what is causing this?

[Member No. 1]

Does the pump start/stop/restart as expected if you plug the pump directly into a wall outlet, hence by-passing the float switch or it's control?

If so then I would speculate you have a faulty float switch/controller.

Not knowing which float switch/controller you have, makes it a little difficult to troubleshoot your problem.
Could be that the float switch/controller has an internal overload that trips from the repeated on/off cycling. Then after a while, it cools down/resets and works until the next on/off cycle.

Just guessing here.

[John Zillmer]

I will try testing that. The control is an Apex Lite, controlling an EB8. The switch is a generic float; I know it works, because I can hear the relay in the Energy Bar immediately prior to the pump not running. The switch also -- when it is not in the feed cycle that I engage when doing a water change -- controls the RO top off pump; that control experiences no similar problem.

[Member No. 1]

So is the float connected to the Apex via a Break Out Box or is it some sort of stand alone device.

Try testing the pump for correct operation as I explain by plugging/unplugging from a standard wall outlet.

If the pump starts/stops/starts as expected, then we can rule out the pump.

Also can you post programming for the outlet on the EB8 that you plug the pump into?

[John Zillmer]

The float is run through a BB box.

I tested the pump, by manually switching the EB outlet on until water came up to the tank, then off until it drained back, and could not replicate the problem.

Here's the programming (there are two switches: one signals water level below which the pump is to run, the other -- placed 2" higher -- is a failsafe to prevent overfilling [these two floats also, with different programming not related to FeedC, control the topoff pump])

Fallback OFF
Set OFF
If FeedC 000 Then ON
If Sw1 OPEN Then OFF
If Sw2 OPEN Then OFF

I've plugged a wattmeter into the relevant outlet, so that next time I do a WC, I can see whether the outlet is functioning properly. I don't recall in the years I've been ignoring this problem whether I confirmed, or simply assumed, that the pump was getting power. I suspect that when I hear the relay switch on I simply assume that means it is feeding power to the outlet.

My suspicion, not knowing much about pumps, is that the backflow of the water (about 30' of pipe, about 3 gallons I estimate) between pump cycles is not something that the pump tolerates. I don't want to hook up a check valve to eliminate this condition unless absolutely necessary, since the failure of a check valve after I refill the SW reservoir would put a couple gallons of saltwater on the floor of the basement.

[John Zillmer]

Update: the outlet works fine. During the failure condition, the outlet is sending 120v, and the motor of the pump is running (it makes a whirring sound, and the case of the motor vibrates lightly). No water is pumped, though.

Iwaki has printed materials that say that if the intake is clogged, the pump impeller can become disconnected from the motor; the magnetic connection can fail. That seems to be a suspect in my situation, for lack of any other obvious cause. I don't have any obstruction, though.

I suspect that the backflow of a couple gallons of water through the impeller might cause this disconnect. I'm going to close the downstream gate valve to maybe 50% flow (the pump is attached with unions and can be isolated with gate valves) to see if restricting the force of the backflow water helps any. If not, I suppose I'll install a check valve downstream of the pump.

If anyone else has experienced something similar, I'd be interested in hearing the details.