Rule LoPro 900S: Why its misunderstood

Rule created the LoPro (low profile) 900 to allow the bilge pump to fit into tight spaces. It is only 2.25 inches high and the outlet can easily be rotated to a desired angle. It can also be configured to kick-in at 2″ or (a very shallow) 1.3″. Mine came configured for 1.3″ and I suspect most folks would want it there. It can also be configured to check for water, by trying to suck some, every 2 minutes. In short it does everything. I wanted it for its low profile and its ability to kick-in at 1.3″.

My objective? To capture the drip from the stuffing box (using a small plastic container) and pump it out. In this way the bilge at large would remain dry. I had a 15 foot run with 3/4″ pipe to get to the thru-hull.


My first problem was that the built-in check valve was not holding the water back. I filled the small plastic container and the pump kicked in and emptied it in short order. The container should take about 3 or 4 days to fill enough to get to 1.3″ but it took just a few hours. The pump would kick in and pump when there was enough water – but no water was coming out of the thru-hull. So it was pumping the water into the pipe, the water was slowly leaking from the pipe and back into the bilge, then the pump would send the same water back up the pipe. This may have been caused by one or both of the following; the amount of water was insufficient to put pressure in the check valve to close it tightly or the built-in check valve was used in an elbow fitting (I gather this combination can be problematic). This would make most folks think that the bilge was filling up from other sources and/or that the pump is working based upon a timer.

Two people I talked to at the marina had this experience and returned the pump to the supplier. I had limited options so ‘I worked the problem’.


My second problem was an inability for the pump to always prime itself at 1.3″ depth. I replaced the elbow with the straight fitting and left out the built-in check valve. I installed an inline check valve about 1′ from the pump. The pump ran but it could not move any water. It eventually time out. I managed to make my plastic container a bit deeper using some tuck tape – just enough to hold 2″ of water. I switched the pump from 1.3″ to 2″ and tried it again. I filled the container several times. The pipe was filled and eventually water started to come out the thru hull. Success!

Check Valve, Elbow yet to be removed.


The pump can switch itself to a 2.5 minute check when its set to work based upon depth. This can confuse folks into thinking that its broken or simply incapable of operating based upon depth (read; no way to avoid regular noise from the pump checking for water pressure instead of depth). The reason why the pump may switch modes is reasonable but an unaware consumer may not care.


If you are going to use the 1.3″ depth setting (the default); do so only if there is a large enough volume of water in the bilge (at that depth) to fill the entire pipe x 2, and avoid the elbow fitting. Even then; I would have to wonder if the pump would reliably prime itself. I would avoid this setting all together.

If you are going to use the 2″ depth setting; do so only if there is a large enough volume of water in the bilge (at that depth) to fill the entire pipe x 2 OR install an inline check valve. Avoid the elbow fitting on the pump. This setting can work well.

While I know that an inline check-valve is not recommended – it seems to be working for me. Also; there is little chance of debris in this application. Furthermore; its not critical. There are other pumps on this boat ready to go to work for serious water ingress.

I am sure I will come back to this to make some improvements/tweaks but for now I am moving on (to finding out why the hot water heater leaks).