I did this project last year when hurricane Irene hit our area in late August of 2011. I live in an area where even heavy rain would cause flooding in the basements. The sump pumps work hard to keep us dry most of the time. I learned my lesson during hurricane Floyd in the late 90s that sometime a pump simply cannot keep up with the incoming water if the ground is totally saturated. So, I thought what if I installed two sump pumps they will be able to pump the water faster. Keep in mind a pump's success depends on availability of electricity of course, to run it and the float switch which turns the pump on when needed. The float should be free of any obstruction in the pit. With that said, I could not house two pumps side by side. So, I came up with this idea of pumps stacked on top of each other. My design below basically has two pumps. The bottom one is a 1/2 hp submersible pump and the top one is a pedestal type. There was no specific reason to choose the top one as a pedestal type. I think the reason might have been the availability of that pump in the hardware store at that time. I also like the idea that the bottom pump will do all the heavy lifting. In case of breakdown or when the water level is rising fast, the second pump will kick in. Since the second pump is sitting higher, it will kick in only when the pit is 60-80% full.
Step 1: Build the Platform to Hold the Top Pump
The pedestal pump's motor can be not be submersed in the water. It is important to keep the motor well above the expected highest water line in the basement in case of heavy flooding. I kept it 18" in my case. I have other safety guards as well, which I will cover later. The center of gravity of the pedestal pump is higher, it is hard to build a stable platform using the household tools. I used 1 3/8" wide slotted straps to build a platform. The platform will rest on the basement floor. I angled it to have a depth of 12". I created a platform using old license plate (rust free). I made sure that I used brass screws to avoid rusting.
Step 2: Place the Bottom Pump in the Pit
If you use flexible PVC hoses for taking out the water as I did, you should keep in mind that when the pump operates the hose gets very heavy with the weight of the water it is carrying. It also shakes violently and rub against the pit housing. As a result within a few months you may see small holes in the PVC hose. To avoid this I wrapped the hose with a piece of foam using duct tape at the point where the hose is expected to rub against the housing.
Step 3: Lower the Platform Into the Pit
Make sure the hose and the power chord of the pump at the bottom have room to move freely.
Step 4: Lower the Top Pump Onto the Platform
Lower the pedestal pump on the platform. Secure the vertical shaft of the pump to the structure of the platform using a plastic tie or a sturdy piece of wire. This will keep the pump from moving laterally on the platform. I wrapped duct tape on to the frame once again to avoid cutting into the shaft itself.
Step 5: Prepare the Outlet to Receive Two Pipes
A little PVC plumbing work was required, so that two pumps could pump water out at the same time. I installed the check valves on the two ends. Check valves stop the water coming back into the pump because of gravity. Here I got some good advice from the experts on Instructables about PVC pipes. Solid PVC pipes should be coupled with PVC cement. PVC cement is a toxic smelly glue like compound. You are supposed to put a generous layer on the both ends which are about to be joined. The compound dries fast, so don't wait too long. I had to use a combination adapter with the check valves, your scenario may be different depending upon the size of the PVC pipe used for taking out the water. Do not forget to use a pipe coupling ring to couple the flexible PVC pipe to the check valve. I also put a thin layer of sealing caulk for a water tight seal at the joints wherever coupling ring was used.
Step 6: Electrical Connections
To make sure that the pumps do not electrocute me in case of severe flooding, I installed two GFI adapters. The GFI adapters are the same devices you see in your bathrooms. These adapters trip when they detect a leak in the circuit due to water. I actually see this safety measure as another challenge. Let us say the GFI adapters trip, how will I know that they tripped unless I go downstairs to the basement every day. So, I am now looking for a device which will sound alarm when there is no power to the pump. I did install a water alarm, which runs on battery and creates 100db sound when it detects water. After one year of usage I found the GFI adapters to be a bit of pain. The ones I used are very sensitive to voltage fluctuations and trip quite often.
Step 7: Secure the Power Chords Against Stresses
Power chords with adapters get heavy. So that they do not exercise unnecessary stress on the PVC pipes on on themselves I supported them with a chord hanging from the beams of the ceiling.
Step 8: Electrical Backup System
Power will go out during natural disasters. Having a portable electrical generator is one of your best options. I did not have any up until hurricane Sandy hit us a few days ago (October 2012.) Please do read my other instructable about making a waterproof housing for your portable generator.