Before you throw out a shower head that just doesn't spray right. Soak it in vinegar and baking soda. Remove shower head. Set in big bowl with spray side down. Sprinkle baking soda into inlet hole (a couple teaspoons should do) now pour vinegar in, enough to cover the head. Watch crud boil away. Soak overnight. Wrap threads of shower inlet pipe with plumbers tape and reconnect.
About 14 months ago, I needed to clean the shower before company arrived, but had just taken a shower. I sprayed the wet shower with lemon juice and noticed when repeating the spraying that it seemed to be working faster than it had when starting with a dry shower. Since then, I’ve been spraying the shower after using it (while still wet) with a light spray of lemon juice. I have not needed to scrub the shower since! All that’s needed is wiping it with a cloth dipped in warm water, and occasionally, a little Soft Scrub when I feel a rough patch where soap scum is starting to build up. This method has also removed the previously nearly impossible to remove stains on the flexible hose and fittings to the shower head and the shower curtain liner.
I’d like to offer a second option as a solution for a chalky, clogged, old showerhead – replace it! In this video, I show you how to remove your old showerhead and install a new one (or the same one, once it’s been cleaned). Note: if you want to salvage your old showerhead, you’ll have better luck cleaning it when it’s off the shower arm so you can get at it from the inside as well.
Norma Vally, the former host of Discovery Home Channel’s series “Toolbelt Diva” and a show on Sirius Satellite Radio by the same name. The weekly column is designed to inspire women – weekend warriors, aspiring handywomen, and even seasoned DIYers – to take on home repairs and maintenance projects with confidence and gusto. Fix-It Friday is an exclusive Women You Should Know® editorial series authored by seasoned veteran of home improvement,

If you are having stubborn stain issues, you can soak the shower head even longer to see if it will blast away.  If you wish, you can use some baking soda and rub that in to the small nozzles with a cleaning toothbrush which will help break down any additional limescale and remove the discolouration.  Rinse it clean and you should notice a difference.  Keep in mind that brown discolouration is ugly (I believe this has to do with iron content in water), but is not harming the functionality of the shower head. Green and white ‘crust’ is what you really need to work on, calcium and limescale are the culprits in clogging your shower head.
Fill a spray bottle with undiluted lemon juice; add a couple drops of dish soap as a surfactant if you want but don’t overdo it; it’s the lemon juice that does the work. Spray all surfaces repeatedly (letting it soak after each application), until you see some results. When you first start, it will appear to have no more effect than spraying water, but, eventually the stains will start to “run”. Once the lemon juice has loosened the scale, you can use a non-abrasive scrubbing pad with Soft Scrub or Bon Ami to remove it.
This is the most sought after cleaning supply that almost every household has for good. Its cleaning capacity has long been established and there are no doubts about it. With that said, cleaning your shower with baking soda; should not come as a surprise for sure. That is correct and all you need to do is to follow simple procedures for accomplishing your goals. 

Open the showerhead holes by soaking the head overnight in a vinegar bath and poking the loosened mineral scale free with a toothpick. Rinse the showerhead in tap water, then reinstall it by applying Teflon tape to the wall pipe threads, screwing it on and tightening it by reversing the technique in Photo 1. Complete the repair by turning on the cold water in the shower and blasting out any remaining mineral gunk to make sure you have a clean shower head.
To remove hard water deposits from the toilet, wear waterproof gloves and use a plastic scrubby square. I tried using a knife, which was effective, but it too easily scratched the porcelain. I used the scrubby on another area, got better results, and no visible scratches. You may also drain the water below the deposit by plunging to avoid any splashing.
Over time, hard-water minerals in tap water build up and clog the spray holes in showerheads. Fix this problem by removing the showerhead and cleaning it. Buy a lime removing product to loosen the scale, or soak the head overnight in vinegar (either white or apple cider). Check the owner’s manual or manufacturer’s website to confirm that vinegar won’t harm the finish.
A quick internet search on how to descale any household object will nearly always lead to white vinegar. Even sensitive items like sterilisers for baby bottles are in safe hands. When using vinegar to descale a shower head, the first thing to get right is the type of vinegar. Malt vinegar isn’t particularly effective and brown vinegar may stain, so white distilled vinegar is best.