Replace your vacuum's HEPA filter for $0.05 (estimated)

I think the HEPA filter in my Eureka vacuum got a little wet once.  Then, the next time I used it, it seemed I was sneezing more than normal. Thought little of it at the time. After a couple more uses I finally started to take it apart to see if there was something going on. Turned out to be the HEPA filter. It was covered in black mold. So, rather than shell out the cash to replace it I decided to go a cheaper route. Bounty to the rescue!
Just one, full size Bounty paper towel = problem solved.
Same quality and micron filtering? Doubtful. But, it works to my satisfaction. The paper towel is readily available, easily replaced, disposable and biodegradable. Maybe splurge and use two for enhanced filtering.

Airflow is good. possibly better. 

Learn how and when to shift gears on your bicycle

If you have been riding a multi-gear bicycle for a while then you have hopefully figured out a shifting style that works. If you are new to pedaling this guide may be of some use.  

Many people use only a couple of gears while pedaling. Unless the area you are biking is limited to one landscape type (i.e. flat, level with no stops), not shifting will be inefficient - a waste of your energy. You might also think of it as not utilizing all available energy (i.e. momentum).
For example, if you are pedaling in a low gear while going downhill you are not adding anything to your speed, in which case you might want to stop pedaling and simply coast along. On the other hand, if you shift to a higher gear you can easily add speed without expending much additional energy. Conversely, if you are in a high gear going uphill you need to work much harder to successfully climb that hill. A lower gear will be slower, but noticeably easier. 

My personal style, while riding on roads in New England, is to try to use nearly the same amount of downward force regardless of the terrain, shifting fairly often to compensate. This works well probably 80% of the time. The remaining 20% will be steep hills, either up or down. As a result of this style I likely shift more often than most. Could be riding motorcycles for thirty years has contributed to near-obsessive shifting.    

I have tried to display the main aspects of pedaling in the graphic that follows. In addition to this visual aid there are plenty of very good resources with written descriptions covering gear ratios and shifting patterns (i.e. pedaling while shifting; not shifting both front and rear at the same time, etc.). See links at the bottom of this post.

The last thing I'd like to mention is that when mountain biking you will get the biggest gains by shifting to match the terrain. Actually, not shifting will not only make it more difficult but also more dangerous. You want to always be able to add some speed when needed. Being in the right gear will help in more ways than one. 

Have fun out there!

REFERENCES: 
1. Home of the yellow-blue-green graphic above.
2. Great written guide
3. A 2nd written guide with added graphics.
4. A very visual guide.

Increase your house water pH for less than $100

UPDATE 2-AUG-2020: just ordered a couple of these "empty filters". This should make the job of adding calcite quite a bit easier. I already have two Big Blue's installed, so I'll be replacing my current 1/2 filter system (described below). This combination is <$50 each, so ~$100 for two. 

- although more costly the 20" filter inside this housing might be a better, more convenient option for your home. This combination would likely cost ~$160.

Project difficulty: 6 out of 10 (for the average handyman)
Maintenance requirements: at least every 3 months you will spend maybe 30 minutes changing filters, cleaning and / or swapping out media (i.e Calcite & Corosex), etc.

Is your water "aggressive"? Does it turn things green (copper degradation)?

This issue may be caused by low pH, not likely a hardness problem. In our case all other measurable aspects were perfectly within expected ranges and we never had scale build-up. Alkalinity was a little off but not nearly as much as pH. After doing the research we realized that a softener would not help.

We had this GREEN issue for several years; green on bottom of bathroom sink, shower floor and around pipe joints and shutoff valves with some corrosion. Then, one day I noticed a pin-hole leak just above the water heater. As I began to replace a foot or two of hot water pipe here and there, I figured I would try to tackle this pH issue before all the copper crumbled! After looking around a bit I quickly realized that I did not want to pay $700, $1000 or even more than that for a system that might work well.

With most things around the house I prefer to take care of it myself, and enjoy doing so most of the time. For this project I figured that I could, at the very least, start simple - a test case. We already had two whole-house filters and had wanted to add a larger third filter for a while.

The Flow Plan: Large filter @ 40 micron sediment > then 5 micron sediment > then 5 micron carbon (chlorine & the like). The overall flow rate is governed to ~2.5 g/min by each of the 5 micron filters. 

Note: we have a lot of iron in the water too, so the extra filtration never hurts. Plus, when it is time to fill the pool, the Big Blue alone works great (replacing the cut half-filter with the full size for high usage / flow rate req's). The two smaller filters have bypass valves to make this very easy.

Now, Do it yo' Damn Self - :-)
Beginning with a basic Pentek Big Blue (as low as $26 if you look around) added to my "system", I moved on to the detail work.

Here is what we wound up with:

                                              Bottom housing of Pentek filter (i.e Big Blue):

The Big Blue will go under the black housing:  

NOTE: be sure to have some extra support because

the added weight of the media will increase load.

The Penetek Big Blue is the 1st in the series of 3-filters

    I took the regular filter for the Big Blue (4.5" x 10") and cut it in half (5"):

                             Next, I cut some tubing and perforated each section (black tubes only),
                             and added a plug to the bottom of each as well:
                                      

                              The perforations allow water to get down and around the media, 

                              to be added in a couple of steps.

                         

                    NOTE: the tube in the middle here was fashioned from spare plumbing parts. That                                  piece holds the filter up at the correct height, while also plugging the center hole                                 which would normally rest on the bottom of the housing, so that it still operates as                                it would normally - if not cut in half.

                                             Time to add some media to the filter housing:

                         Add a little Calcite and some Corosex, slowly, mixing them together beforehand or                              during. As you add it, be sure to keep the black tubes touching the bottom.

                         Depending upon your pH you might want / need more or less Corosex.                                                  Recommendations are usually for 90 / 10 mix. Corosex breaks down faster 

                         and is capable of raising pH to 8.5 (too high).

Each tube shown, three perforated and the center support, all sit at the same height <5" -  no more than 1/2 overall height. The half-filter goes on top and then the housing is screwed on - tightly. You probably just want to keep on going until it cannot go any further. The filter will "smush" onto the 4 tubes. This setup allows water to flow around filter, into and through the media, getting as much exposure as possible, without concern for the eventual "chunking". Larger, purpose-built systems have backwash capability to clean and mix the media. If you let it set for too long it all begins to stick together. The large systems expect flow rates of as high as 9 g/min. Since this system is restricted to 2.5 g/min, contact time with the media should be sufficient.

OUTCOME:
Our original pH was around 5.7, so it needed to come up quite a bit to 7 (neutral), or a touch higher. After some experimenting I found that a mix of 70% Calcite / 30% Corosex worked best. My theory is that there is substantially less media here vs. a more commercial system with backwash capabilities. I change the filters every three months or less anyway (lots of sediment / iron), so washing / exchanging the media at that time is not a huge issue.

Using 3-different pH kits we had varied results. Fortunately, my wife is a Scientist, specializing in Mass Spectrometry, so accurate measures were not difficult to come by. We think it averages about 6.8 - initial, after trying ~80/20 mix - a significant increase over the original low of 5.7. If I make any changes I will add another Pentek - the bigger blue (4.5" x 20"). Cutting that filter to 3/4 length would allow for more filtering with the same amount of media.

Important: To raise pH to 7 or above I added 1-2 tablespoons of Corosex to the 2nd filter housing (outside the filter, of course), waited a day and measured. The smaller filters have independent shut-offs and do not have high pressure similar to the Big Blue. Overall they are easier/quicker to remove. An added benefit is visibility, as the housings are clear. Once desired results are achieved you can see how much Corosex is in there, and more importantly, see how long it takes to breakdown or "chunk".

Media:
Calcite from Freshwater Systems
Corosex from Aqua Science 

Learn more about dosage / usage, and more here (no affiliation, just a great consolidated reference page with FAQ).

Cost / time breakdown
Pentek Big Blue Filter $26 - $60 (shop around, try ebay, etc.)
>>>> Try to get one WITH the pressure relief valve, or plan to allow another method to relieve pressure. It is much, much easier to unscrew without pressure. 

Parts to add Big Blue filter to existing filter "system" ~$20
Calcite: ~$40 - $60 for 50lbs.
Corosex ~$18 for 12lb "sleeve"/bag
Black tubing $.90 @ Home Depot
Random parts for the center tube were "free" for me, but original purchase price ~$8
Total: $90.90 - $120 (keeping in mind that the media will last for quite a while, so the cost could be amortized, resulting in initial layout of $15 - $20, lowering the startup costs to well-below $100).  

Hours spent:
Adding new filter: < 1 hr
Experimentation ~3 hours over the course of a week (adding media, waiting, testing)
Cutting & perforating black tubes < 20 min.
Total: 5 hours at most

Final Note:

This type of system is not ideal, and certainly not maintenance free. We have only 4-people with a total of three bathrooms. A larger house and/or number of people will likely require more filters in series or a big system, such as this one from the Clean Water Store (no affiliation). 

Happy Plumbing!