PERFLEX SWIMMING POOL FILTERS:
How We Use Them For Sap

Prepared by: Bill Hubbert,
Hubbert's Maple Products, Sundridge, Ontario

FILTER SIZE
When purchasing a DE sap filter, get the larger unit. The only disadvantage with the larger unit is that when you go to clean it, you have to dump out a larger volume of sap that is trapped within the base. The larger unit increases the time between cleaning; and this is a huge advantage.

PUMP
I started with a 1/3 hp jet pump, as this gave me over 600 gal/hour, which exceeded the capacity of my evaporator. When we added an RO, we increased to a 3/4 hp unit to increase flow to over 1,200 gal/hour. You will want your pump flow to at least exceed the rate of usage, and  a higher capacity is even better. Working pressure is best to be at 15 psi or, ideally, even lower. Higher pressure will result in dirt being pushed through the unit.

CONFIGURATION
Previously, we had our unit between the large storage tanks and the feed tank for the evaporator; and we would filter from one storage tank to the other if the sap was to be stored prior to use, or directly to the feed tank if it was going to be processed immediately. Under our current system, we never pump directly through the filter to the feed tank; we now put our sap through an RO on its way to the feed tank. We now use three storage tanks, with the sap pumped through the filter from the initial storage tank to one of the other two, where it feeds the RO.

USE
When we are assembling the filter after each cleaning, we fill the base half full of sap and put the DE in prior to bolting the top on. The instructions for our unit (75 gal/minute) call for 7 pounds of DE but we find that less than half that amount works well for sap (about 3 liters). Less DE is better for the first pass when the sap is cloudy since otherwise the unit plugs up very quickly. Use of the unit is the same as a syrup filter press in that you initially start pumping the sap back into the tank you are drawing from until it looks clear, and then you can redirect it by turning a valve on to another tank. If you are using a pressure pump, it would be a good idea to have a relief valve in the system; in case someone forgets that you ALWAYS need at least one valve on or you will break the filter.

CLEANING
When the pressure builds up, you can shut the pump off and bump the handle to realign the DE and start it up again. Once this no longer works, the unit needs to be cleaned. The best method is to take it apart and hose down the filter elements to wash away all the old DE. After rinsing the base, bolt it back together, putting the DE in as described above. We find this can take close to half an hour by the time you complete all steps. We now use a quick method for those times in the middle of the day when we do not have time for a complete cleaning.

SOME TIPS

1. Make sure the unit is located where you can keep an eye on it, as pressure tends to build quickly; and, once the pressure starts to build, you need to check on it
   frequently.
2. Cloudy sap towards the end of the season will benefit from more than one pass. We put our end of season sap through several times before processing; starting with less DE so that it will go through easier on the first couple of passes. No matter how cloudy the sap is, you can make it clear with enough passes. The last few days' sap will be even clearer if you add more filter aid with each additional pass. I have put sap through up to six times, increasing the filter aid load up to 8 liters by the last pass, and the sap was clearer still. When sap flows decrease at the end of the season, we spend all day pumping the sap back and forth between two storage tanks. When it is clear, we pump it into a third and hold it there, often for several days until we have enough for a boil.
3. We have a small 30 gal tank (new laundry tub) plumbed into our system just before the pump. Rather than take the unit apart, we turn all valves off and bump the filter handle to loosen the DE and drain it out, discarding it down the drain. You can pour hot water down the outlet of the sap filter to flush it even cleaner. We then turn the valve on at the storage tank and open the valve at the bottom of 30 gal tank, so that the pressure from the storage tank sends sap into the 30 gal tank. We then close off the sap storage valve, stir the DE into the smaller tank, and pump it into the unit to start filtering right away.
4. During the last season, we started using two DE filters, each on a separate pump. We can pump from the initial storage tank to a second holding tank through one filter, and then pump from the second storage tank to a third with the second unit, at the same time. This allows us to give the sap two passes simultaneously without waiting to boil. The other advantage is that when the pressure gets high on the first pass; it is not as crucial, as we capture any dirt on the second pass.