Finding the right 12v pump for your UV water filter system in your
boat, rv or off grid cabin.
A common question that I am asked is "what 12v pump do you suggest for my boat or Rv?" When looking for a good pump for your new UV water filter systems there are a few questions to consider. What gpm of water will your UV system treat? Are you using the standard carbon block filters or a high flow filter set? What is the power draw up the rv/marine pump you are looking at. Here are some steps to determine what pump you will need.
Step 1. Determine the flow rate your UV system can treat. WaterFixer Model 1000 UV Systems treat up to 4gpm. Cur-rent SafH2o UV filter systems treat up to 3gpm.
Step 2. Know the limits of your filters. Both UV Systems use a .5micron carbon block filter as the pre-filter before the UV sterilization chamber. This .5m carbon block filter will slow the flow rate of your treated water down.
Step 3. The truth about 12v rv and marine pump gpm ratings. 12v Rv and Marine pumps are rated for their gpm in a testing facility that has no resemblance to real life. They gpm rating does not account for any variables such as line loss, fitting size, suction/lift height, head/rise or filter backpressure. All of these will cut the gpm of your 12v rv pump down. Let me explain those terms.
Line Loss - When water flows through pipe the walls of the pipe create friction against the water molecules. This friction causes the water flow to slow down or loose speed. The smaller the line means that the line loss will be greater.
Fitting Size - This is pretty straight forward. If you have small fittings in your water system the flow rate will be reduced sometimes significantly.
Suction/Draw/Lift Height - How high your pump is above your water source. Rv and Marine pumps cannot suction lift water very high.
Head/Rise - How high your 12v pump can pump water. Rv and marine pumps can pump water quite high, but loose pressure and flow as they do.
Filter Backpressure - How much pressure it takes to push water through a water filter.
Step 4. Oversize your 12v Pump. After looking at the variables above you will see the need to oversize your 12v pump above the gpm treatment rating of your UV filter system, especially if you are using a .5m carbon block filter. If your unit treats 4gpm you will want to have a 5gpm 50 psi pump to get all that water through. 3gpm unit should have a 3.5 gpm 50 psi pump. If you are not concerned about reaching maximum flow rate you can have a lesser pump. If you are us-ing a 1m high flow filter you can use a lesser pump in many situations.
Step 5. On Demand vs Variable Speed 12v Pumps. This is very important. YOU CANNOT USE A VARIABLE SPEED PUMP WITH A UV FILTER SYSTEM!!! The backpressure of the filters will destroy the pump, in days or even hours. YOU MUST USE A STANDARD ON-DEMAND RV OR MARINE 12v PUMP.
Step 6. Locating the 12v pump in your water system. 12v marine pumps are designed to push water, not pull it. They do a great job of it. They are very bad at pulling/drawing water. The rv or marine pump should always be before your UV water filter system. It is best to put the 12v pump near your water source.
Step 7. Soft Pipes. When installing your water system it is best to attach the pump to the UV water filter system with non-rigid pipes. If you use rigid straight pipes from your pump to your UV water filter system and the distance is less than 6 feet the vibration of the pump might cause fittings on the filter system to come free and leak.
Step 8. Choose your Wire Size. Check the amp draw on your chosen pump and make sure that your 12v power source and wiring on your boat or RV can supply the correct amps for your pump. If your 12v pump and 12v UV water filter sys-tem are connected to the same wiring be sure that both can be powered when the pump is at maximum amps. If your pump overdraws and 'steals' power then 12v ballast on your water filter system will be the first to burn out.
Step 9. Check for leaks. I suggest doing this a few times the day of the installation and every few days soon after the system is first installed. If you hit some rough road in your Rv or rough seas in your boat it is always a good idea to check your pump and water system again.
Step 10. Do a bucket test. What's a bucket test? It is a way to measure how much water is flowing through your filter system. Take a bucket and measure how long it takes to fill it up. If your system treats 4gpm a 1 gallon bucket should take 15 seconds or less to fill up. 3gpm treatment should fill a 1 gallon bucket in 20 seconds or less. IF it fills up faster you will need to limit the water flow through your UV system by installing a shutoff valve and turning it down until you reach the desired water flow.
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