The toilet seems to run every now and then for no reason

Nah, that doesn't sound like the toilet or sink were hooked up wrong, your sewage tank is probably full, you can have it pumped out for $100 or so. They fill up every so often for w/e reason.

The most common reason for a toilet to continue to run is a problem with either the flapper or the entire flush valve itself. The water is slowly draining so the fill valve keeps running.
The flapper is the least expensive and easiest solution, so start their. It's usually around $5. If that doesn't solve the problem, I would purchase a flush valve kit, around $20, and replace your flush valve.
*Note: If you have to replace the flush valve, you have to take your toilet apart. Start with the flapper.

There could be several reasons why it won't refill. It could be the fill valve, which can be replaced with a standard fill valve located at any hardware store. The more likely reason is the stem inside the shut-off of the toilet has broken off inside the valve. This is very common when a valve is older and usually doesn't get shutoff. If this is the case, a new shut-off valve must be soldered on.

The flapper ball may be contaminated and not sealing or the float level has changed and needs adjustment. You should be able to see if the overflow has water flowing into it continuously.

try bending the float rod slightly...

Any brand approved for septic should work well in the saniflow system, but the key is to use as little as reasonably possible and flush as you go. Big wads of any type will compromise the system.

Hi,
The flapper is bad....and allowing water to go through into the bowl very slowly...You need to find the correct flapper for that toilet....even all Mansfield toilets can have different guts inside....then replace the flapper which is very easy to do...

heatman101

Typically your pump should only operate when the float reaches its set point. Check and make sure that the flapper valve isn't leaking into the toilet. I think also there might be a condensate line draining into the pump from the A/C condenser if the unit is in the attic area of your home. You can check that by flowing the drain line from the condenser to where it either drains to the out side or to a drain system on the interior of your home... Good Luck! (Also stay safe when entering the hot attic this time of year----Let someone know what your doing and where your at for safety reasons!!!!)

Problem solved.  Reason was a totally blocked waste line that resulted in toilet malfunction.  Toilet functions normally now with removal of blockage.