At times my bathtub will drain very slowly, after using the plunger on it will clear up for about a week, then it will become slow again. Other times I will wait for the tub to drain completely and then pour some draino down the drain and for the next week it will drain quickly. Again after a week or so, the tub will drain slowly again.
Tid: Hair and organic material like soap and debris associated with normal bathing is easily disolved with strong caustic materials like Draino and flushed away. It is the heavy materials like like sand and other inorganic things that sink to the bottom of the trap beneath the tub that can cause a chronic off and on stoppage situation with the tub, it slows the flow of water passing through the trap and causes a log jam by slowing down the needed velocity to keep the trapway clear. This heavy material is unable to make it’s way out of the trap with just the normal flow of water flowing from the drain. It can be forcefully flushed from the trap with a strong flow of water from a hose pushed down the over flow pipe located behind the tripever. An easier way is to use a good strong wet/dry type shop vacuum and suck the stuff out through the drain opening in the bottom of the tub. A damp rag stuffed into the overflow is needed to direct the vacuum’s force down to the trap. Care should be taken that the damp rag is not allowed to be sucked down the over flow pipe. MOE