Most pool owners have an automated pool cleaner.  You know, the ones that automatically clean the pool while the pump is running.  Some run on the positive pressure of the water being pumped back to the pool.  Most are attached to a series of vacuum hoses made long enough to reach all corners of the pool.  This hose is commonly plugged into the skimmer line which creates the vacuum allowing the cleaner to work.  The skimmer will allow debris to be cleaned from the pool bottom this way, but now unable to perform it’s main function. It was designed to skim the debris off the water surface before it even has a chance to sink to the bottom.  In addition, all the extra wear and tear from this hose being plugged into the skimmer day after day can also cause it to crack and leak. The problems with running this hose through the skimmer can be solved with a dedicated pool vacuum line.  Ideally this line should have it’s own valve when it’s plumbed into the suction side of the pump.  With this valve, the amount of vacuum available to the cleaner can be adjusted.  This helps to prevent the cleaner from climbing too high up the pool wall, where it can suck in air which can cause the pump to lose it’s prime. When this hose is run through a dedicated vacuum line, it frees up the skimmer to clean the water surface.  It also reduces wear on the bottom and sides of the skimmer. Another benefit is that manual vacuuming of the pool is much easier and effective if you can attach this hose directly into the vacuum line instead of inside the skimmer. When we pressure test the pool plumbing, we find that many pools were built with this dedicated vacuum line already piped in, but stubbed up near the pump.  This line was never plumbed into the suction side, but available if someone wanted to do so. A vacuum snap-cap is an insert that screws into the dedicated vacuum line wall fitting. This cap is under spring tension so that it can be lifted up and the vacuum hose fits inside.  If the vacuum hose is ever pulled out, the cap snaps shut.  This greatly helps to prevent any safety issues.  But if the spring or cap breaks, the entire insert should be replaced immediately.