The threads are stripped on the drain plug of my Hayward Sand Filter. Cap will not go on tight enough to keep it from leaking. Does anyone have any ideas how I can fix it and not have to buy a new tank?

Sounds like your threads are stripped or the plug is the wrong one.

I'd try some teflon tape several turns, after you remove it and verify the threads match and are not stripped.

Although rare, there is such a thing as the tank being cracked, as well, at the drain hole.

For most applications, there are "oversize" screw plugs available at some car parts stores.

God bless your efforts.

Either the tank canister has cracked, (probably from ice damage), or your drain cap is missing, loose or cracked.

Are you sure it is leaking from a spot "Originating" at the bottom? Many times this is what is seen, but the water is actually traveling down the side.

If at the bottom, you either have a cracked tank, or the drain cap is loose, missing the cap gasket or it is on "Cross Threaded"?

But... most likely from experience, it leaking at the valve clamp.

Hello, 1 You need to unscrew the drain plug and screen (if it is still there!) at the base of the filter. 2 You can reclaim most of the sand by letting the filter drain through a sieve (lots of work) or use new sand. 3 Uncouple union joints or couplers that attach to filter head. 4 Remove filter head. 5 You can try pulling some sand out of the top. However, do not damage the filter fingers in the sand. 6 Use a hose to blast the sand out the bottom drain. 7 Inspect all fingers, replace if necessary. 8 After all is cleaned out, place finger mount inside filter. Cover top of mount with a cup or similar to keep the new sand out of the finger assembly. 9 Replace drain plug and screen. 10 Fill filter halfway with water. 11 Slowly pour sand in and spread evenly. 12 Remove mount cover. 13 Reinstall head, unions and couplings. 14 Prime pump and test for leaks.
Good Luck

Usually in th bottom of the filter you have two parts. The first is a piece with a screen that threads into the plastic housing. The second is a Cap with a rubber washer inside. Make sure the rubber washer is there. Do not overtighten the drain into the houseing

IF IT DOES NOT FILL CONSTANT FROM POOL IF IT IS AN INGROUND YOU WILL HAVE TO HELP IT BY PUTING A GARDEN HOSE WATER ON IN SKIMMER PUT A RAG AROUND HOSE FILL CUP TURN OFF RETURNS OPEN BLEEDER VALVE ON FILTER LET WATER FILL START PUMP AND OPEN RETURN VALVE SLOWLY YOU MAY HAVE TO DO THIS SEVERAL TIMES MAKE SURE AFTER YOU GET WATER FROM BLEEDER YOU CLOSE MAKE SURE ALL CONNECTIONS ARE TIGHT INCLUDING CLEAR CAP ON PUMP THESE ARE AIR BLOCKS IF ABOVE GROUND CHECK ALL HOSES AND CAP

There are a couple of ways to do this repair, First way is to buy a reducer bushing (threads on the inside and smooth surface on the outside), drill out the hole to tightly fit the bushing, and prime and glue it in place. The second way is to buy a tap (the next size up), buy a brass reduser bushing with threads on both the inside and outside. If you dont have enough material to inxdease thr hole size, then you will need to buy some J.B. weld and fill the hole, wait 16 to 25 hours to drill and tap

I've had the same problem every year since I bought this house 10 years ago with my Hayward filter drain and finally MacGyvered a great solution. Went to Home Depot and bought a 1" PVC shutoff valve. The Hayward drain has an outside 1 1/4" thread. The part I got was an 'Aqua-Dynamic' 1" PVC Schedule 40(I can't find a picture of it on the internet). It is a white PVC valve with an inside thread that mates with the Hayward and a red shutoff winged knob. You need to hacksaw the red wings off the knob in order to be able to screw it onto the drain because the filter's base gets in the way. Leave the valve in the open position(especially if water is still draining with filter off) and put PVC cement on the outside of the drain thhreads and a bit on the inside of the valve and screw it on. When the glue dries(5 minutes), you now have a drain that you can open and close every year with ease(you need a pair of pliers because the wings are off the turn knob but it works great!)