No lights are on and system does not open valve to let water run into pool

make sure everything is hooked back up the correct way

i am not completely familliar with this system but i am pretty sure that opening the relief valve should allow water to exit providing all the valves are open. as for green pool, if the water is not moving, you will not be able to clear the water.

Hello... Is this your first pool? If so, do you have a local pool chemical supply company? They will test a sample of your pool water with way better equipment than the test strips... Than they will tell you exactly what you need and how to apply them... This is my 4th year with this salt system and 18'x 4' intex pool... Starting them up is tricky and it still takes me weeks to get it right... But the pool store told me how to start it up for next year so hopefully it won't take as long...
The phrase backwash referes to cleaning the filter... With the intex filter/pump system, that is the filter cargtridge that inserts into the pump/filter housing... Close the pool valves, open the filter cartridge housing, take the filter out and hose it down with a garden hose... Before you return the filter, dump out the nasty water sitting in the filer/pump housing... the Return the filter, screw back on the cap, open the pool valves and open the vent screw on top of the filter cartridge housing lid... This allows the pool water to flow back into the filter/pump and removes unwanted air pockets in the hoses... Once the water flows out of the vent screw, screw it back down to stop the water coming out... Now your down backwashing the filer...

Hope this helps,
Dan

What check valve?
if there is a check valve plumbed into a plumbing system, when pump comes on, then yes, check valve will automatically open!
its a one way valve! The water will flow against the flapper, pushing it open!
you have no control over that! And... Water always goes thru the heater! Whether it is firing or not / on or off, does not matter, if pump is on, water is also flowing thru heater.

make sure the valves on the outside of the pool are closed so when you open up the valve to change the gasket the pool water will not continue to run out of the filter.
Once you are secure about water flowing out of the pool through the filter you can remove the bolts holding the filter body together and change the gasket.

Rod
US Parts Center

red valve handles align with flow of water long ways the tail in direction of pipe valves open to open pool generally all Valves open Main drain (floor of pool). Skimmer square hole somewhere on side edge of pool... There could be a third Valve for a seperate Vacuming port (like mine) it can be either its below water line .. On the Round Sand filter theres a Multi port Valve I usually start the Filter in RECIRC mode .. While I net and gather debris then I add floculant leave on recirc two hours . Then Shut ALL down for 12 Hrs while all the algae and debris sinks to bottom . Water will be reasonably clear.. Make sure pools Extra full , And Vacum all on bottom on waste setting

From the users manual for these pool cleaners:

The Pool Pulse is a flow meter that measures the volume of water flowing through your Zodiac cleaner. It must be used to properly set the flow and can be used as a diagnostic tool when the cleaner isn't running properly.For the following steps, using 2 people is recommended; one poolside and the other at the plumbing manifold. Vacuum and skimmer valves are located at your plumbing manifold.
• Remove the cleaner head.
• Attach the Pool Pulse® to the end of the hose and keep it under water as shown in Figure 1.
• Turn on the filtration system.
• For pools with one skimmer, flow is automatically regulated by the Flowkeeper Valve. Insure the blue indicator of the Pool
Pulse is in the ideal range (when viewed from the side).
• For pools with two or more skimmers, leave the selected skimmer open and slowly close the other skimmer(s) until the blue
indicator of the Pool Pulse moves into the ideal range (when viewed from the side).
• For pools with a wall vacuum fitting, leave the wall vacuum fitting fully open and slowly close the skimmer valve until the blue
indicator of the Pool Pulse moves into the ideal range (when viewed from the side).
• Keeping the hose under water, remove the Pool Pulse. Submerge the cleaner head, and when the bubbles stop coming from the
extension pipe, attach the hose end. Your installation is now complete.

I happen to have a copy of the users manual for this pool filter. These are the instructions for operating your filter.

1. Be sure correct amount of filter sand media is in tank and
that all connections have been made and are secure.
2. Depress Vari-Flo control valve handle and rotate to
BACKWASH* position. (To prevent damage to control valve
seal, always depress handle before turning.)
3. Prime and start pump according to pump instructions (be
sure all suction and return lines are open), allowing the filter
tank to fill with water.
WARNING: ALL SUCTION AND
DISCHARGE VALVES MUST BE OPEN WHEN
STARTING THE SYSTEM. FAILURE TO DO
SO COULD CAUSE SEVERE PERSONAL
INJURY.
Once water flow is steady out the waste line, run the pump for
at least 2 minutes. The initial back-washing of the filter is
recommended to remove any impurities or fine sand particles
in the sand media.
4. Turn pump off and set valve to RINSE position. Start pump
and operate until water in sight glass is clear—about 1/2 to 1
minute. Turn pump off, set valve to FILTER position and
restart pump. Your filter is now operating in the normal filter
mode, filtering particles from the pool water.
5. Adjust pool suction and return valves to achieve desired
flow. Check system and filter for water leaks and tighten
connections, bolts, nuts, as required.
6. Note the initial pressure gauge reading when the filter is
clean. (It will vary from pool to pool depending upon the
pump and general piping system). As the filter removes dirt
and impurities from the pool water, the accumulation in the
filter will cause the pressure to rise and flow to diminish.
When the pressure gauge reading is 8-10 PSI (0.55-0.69
BAR) higher than the initial "clean" pressure you noted, it is
time to backwash (clean) the filter (see BACKWASH under
Filter Control Valve Functions.)

you probably have a check valve (back flow preventer) on the line that supplies water to the spa when the pool is filtering as normal. Your check valve may have some debris in it or the seal inside may have failed allowing the water to drain into the pool when the system is off. You should see a valve on the return line that splits off from the pool return line on your system. There are several different check valves on the market, some have a clear lid that you can inspect without taking it apart. Some of them cannot be taken apart. Your challenge will be to find the check valve, then try to check to see it debris may be holding it partly open or it the rubber seal inside is damaged or missing. I hope this helps.

Make sure thermostat is set higher than water temperature. Make sure pump is running and water is flowing through unit. If gas valve is not opening then flame sensor or gas valve is bad.