Cheap compressors fail, and it seems that intake or pressure reed valves on the pump head fail quite often. Finding a replacement valve kit might be impossible.

A reader writes in that he made his own valves using the blade from a paint scraper, rough cut and ground to size, to fit his compressor pump, and for him, the fix worked perfectly. He also pointed out that it was important to pick a paint scraper with a blade that was the same thickness as the original valve material was.

A creative solution, for handy folks, when they need to replace a compressor pump valve, and can’t find an OEM or off brand part.

Panel Mount Pressure Gauge

The things you want to look when selecting a replacement air pressure, or air regulator pressure gauge are:

• same size gauge face
• same (or close) pressure range displayed on the gauge face
• same size mounting thread or style
• same mounting position (back or bottom)

For a DIY type home air compressor, another indication that you have selected the right gauge will be the price. Expect to pay under $15 for an air pressure gauge for use in a general purpose, low end air compressor.

Replacement compressor air gauges are available at most decent hardware stores, and certainly should be available in the parts section of the store from which you purchased your air compressor originally.

If you are using industrial type air compressors, you can expect your compressor supplier to have a full range of spare parts for you, including any gaskets you may need.

This will likely not be the case for the lower cost, DIY type air compressors, that are being sold by the thousands from big and small box stores throughout North America (and the world??). What to do if you need a gasket?

Recognize first of all that a compressor pump head gets very, very hot in operation. Yes, you can burn skin with the heat generated, so any gasket material has to be heat resistant.

What some visitors to my about-air-compressors.com info website have done is as follows.

They acquired gasketing material. They disassembled the pump and located all the gaskets that were present. They then either removed them to use as a template to make new ones, or used the surface where the original gaskets were installed as a template, if the gasket was beyond removal in one piece. With the old gasket template as a guide, they marked the new gasket material appropriately, and cut the material to suit.

If your air compressor won’t build pressure past a certain point, the most frequent causes seem to be either the intake or high pressure reed / flapper valve is failing, or a gasket is letting go. You may, nor may not, be able to see the failure point if it is the gasket. Yet, once you have the pump apart, you might as well eliminate that as the potential problem, by installing new gaskets.

If you can’t buy them, you can make your own.

I have not dealt with the company myself, but a source that has popped up for gasket material is:

www.federalmogul.com/en/AftermarketSolutions/NorthAmerica/SealingSolutions/Brands/Fel-Pro/

I don’t think you can buy from them, but you can find the material and a source through them, evidently.

No compressed air that is coming from an industrial or DIY type air compressor is suitable for breathing.

Having said that, you can add sufficient air-treatment equipment to an air circuit from an industrial air compressor that will prepare the air for human consumption.

If you wish to do that, check with your local regulatory or specifying body to research and to find the type of compressed air treatment equipment you must add to the air supply, to make normal compressed air suitable for breathing.

Otherwise, if you are contemplating breathing air from a mask that is being supplied by non-treated compressed air, you are risking your health, if not your life.

The first is that the pressure switch has malfunctioned. It is supposed to trip off when the tank pressure reaches the set point, cut power to the motor, and that stops pumping air into the tank. If the pressure switch does not trip off when the pressure in the compressor tank reaches the correct set point, then the pressure switch has failed, and needs to be replaced.

Or, if the air pressure in the tank does not ever get to the pressure switch out pressure level, then your air compressor will never shut off. There are many reasons why an air compressor will run, and run, and run and never reach the cut out pressure setting.

Both issues are addressed in detail on the website. Visit the site, click the site map link, and look under Troubleshooting for lots of information about why your air compressor will not shut off, why it will not start, etc. etc.

Compressed air flowing through an air line, whether a rubber hose, a PVC hose, a copper pipe, or black iron pipe, encounters resistance as the air flows along the inner surface of the air line. This slows the flow of compressed air at the edges, yet the air in the middle of the air line is not as affected. This creates turbulence in the compressed air, increasing resistance to flow. The result is flow loss and pressure drop at the air line exit.

If you started with 100′ of 1/2″ rubber hose, and pumped air at 100 PSI into one end of it, you would not get 100 PSI out the other end. It might be close, or quite bit less, depending on the smoothness of the inner air hose surface. Add another 100′ of hose and your pressure at the end of 200′ of run would be less, even though you are still pouring a constant flow of air at 100 PSI into the end. Make the hose longer still, and the yield at the end of an even longer air line would be less.

Then, if you add elbows, angles and tees to the air path, each time you do, you increase resistance to flow, and this costs you in flow and pressure at the point of use.

What can you do about it?

Increase the diameter of the air hose to reduce flow and pressure loss due to turbulence. Keep the number of air fittings to an absolute minimum. Increase the air pressure entering the hose. Starting with a higher air pressure means, even though you will lose flow and pressure due to turbulence in the air line still, the higher the compressed air pressure at the hose beginning will mean more higher pressure and flow at the end.

In order to fill tires, you need a compressed air source. In this case, let us assume that it is the home air compressor that is being used?

What is the air pressure in the air compressor tank? Typically, a smaller air compressor will run until the tank pressure gets to 100-150 PSI, somewhere in that range. Let us assume then that our air compressor has run up to the cut out pressure, and we have 120 PSI in the tank.

Having pressure in the tank is important, as compressed air flows from areas of higher pressure to areas of lower. If the pressure in the tire was, for example, 35 PSI, and the compressor tank had only 20 PSI in it, and the air compressor was not running, the air would flow from the tire back into the air tank through the air hose!

With a fully charged compressor tank with 120 PSI in it, we will need to connect an air line to the compressor discharge coupler, using a connector that fits that coupler. At the other end of the air line will be another coupler. The coupler will not let air flow out until a mating connector is inserted.

You have a tire chuck? That’s the small tool that fits over the valve stem on the tire, when it is pushed down onto the valve stem, air can flow through the tire chuck into the tire. So, you need a tire chuck, and you need one that can have an air connector threaded into it, since without the air connector, you will not be able to attach the tire chuck to the air line from your air compressor.

Air line connected to the discharge coupler and tire chuck installed on the other end of the air line? Good, now, push the tire chuck down onto the tire valve stem. You may have to remove a threaded cap off the tire valve stem first.

Careful!

You are now blowing compressed air at 120 PSI into your tire which will way over pressurize the tire. What pressure do you want for that tire when it is full of air? How will you know that the tire is full to the correct pressure?

Two ways.

One is to set the regulator on the discharge pipe from your compressor tank to the tire pressure setting you want the tire inflated to. If you set that regulators to, say, 40 PSI, and the air tank has 120 PSI air in it, the regulator will reduce the pressure flow to the tire to 40 PSI, or whatever pressure you set the regulator too.

The other way, and the one I use, is a tire pressure gauge. I watch as air is flowing into the tire, and when I think it’s getting near fully inflated, I pull the tire chuck off the valve stem, and instead, push the tire gauge onto the valve stem. It immediately shows me the pressure level in the tire. If I need to add more air I do, or if I have put in a bit too much air, I open the tire valve a bit (pushing down on metal button in the center of the valve stem) to bleed off air. Then I check the pressure again, until I have it set correctly.

A pressure regulator on the compressor may have a 2-5 PSI over or under range, so that’s why I like to check the tire pressure with a tire pressure gauge.

Got any questions about using compressed air? Just ASK!

This means that the gauges are not built to handle heavy, prolonged use which might break a gauge needle,  and they will fail due to internal corrosion or mechanical fatigue. That might take months or years, depending on the use and the condition of the compressed air the gauge is monitoring.

Further, for many of us, our air compressors are relegated to the basement or workshop where things pile on them, other things run into them, and ultimately the gauge face gets cracked or the entire gauge might get broken off.

Time to replace your air gauge? It is pretty easy. Here is how.

There Are Two

First, know that most DIY type air compressors come with two gauges. One of the gauges is to give you a reading of the air pressure in the compressor air tank.

The other gauge is normally found as part of the regulator assembly on the discharge line from the tank to the outlet coupling. This gauge is to show you the pressure setting on the regulator, and shows the air pressure for your downstream application.

Configurations

As depicted in the photo at left, the air gauge has a face on which the pressure range for that gauge is visible. That scale is protected by a carbonate or glass face, which is susceptible to breakage.

The diameter of the standard air gauge face is 1 1/2”. Another air gauge standard diameter is 2”. Yours is likely one or the other, and I would lean to the 1 1/2″ size as being typical, as it costs the manufacturer less money to install a smaller gauge on an air compressor.

The gauge will be equipped with a male thread fitting on the bottom or the center of the back. It does not matter to the gauge whether it is turned into  the air line from a male thread on the bottom of the gauge, or a back located male thread.

The different locations of the mounting threads are purely for the convenience of the installer or the location of the air line into which the gauge is threaded.

You can also purchase air gauges that are panel mounted to facilitate an industrial type installation. A panel mount gauge typically has a back mount, and comes with a space ring that allows the gauge to fit into a through hole on the panel, without dropping completely  through. An installer may have to run an air line to the back of the panel mounted air gauge.

Pressure Ranges

The typical DIY type compressor air gauge will have a pressure range of 0-160, maybe 0 to180 or even 0-200 PSI.

As long as the air gauge you obtain as a replacement shows the normal cut in pressure level of your compressor, and the normal cut out pressure level, that it is a 180 PSI versus a 200 PSI really makes no difference.

Specialty application gauges will have different pressure scales on them, depending on the application for that gauge.

How To Buy

If your old gauge is in good shape  (or even if it is not) take it with you to the shop so that you can match-the-hatch and get the same size fitting, same sized face, and same pressure range.

<p>If your new gauge is a back mount type, and your existing gauge has the fitting on the bottom, the new gauge may not fit. It is always good to get the same size and style if at all possible.</p>

<p>If your air gauge is totally gone, opt for a 1 1/2” face, 0-200 PSI pressure range, with a 1/4” male NPT fitting on the bottom. That is a pretty good fit for many DIY type air compressors.

<h3>How much? </h3>

The new gauge will set you back somewhere between $5-$15 or so, depending on where you buy it.

If the gauge is priced more than that, it is possible you are buying:

• a) an overpriced air gauge
• b) a much better quality air gauge than needed
• c) a specialty gauge of some sort
• d) a different compressed air component entirely

Doing The deed

Make sure you unplug your compressor and open the drain valve in the tank to empty the air pressure completely. Else, when your air gauge gets down to the last thread, one final turn will shoot that sucker right up and out of your hands, as the air pressure in your tank blasts to atmosphere. Be careful!

Some gauges have wrench flats to use a wrench, some rely on you turning the body of the gauge to unscrew the thread. If the gauge is not broken before you do this, it quite likely will be after you do so!

Anyway, unscrew the old gauge after you double check that there is no air in the compressor tank.

Use pipe dope or teflon tape (better the former than the latter as far as I am concerned) to coat the threads on the new gauge.

Turn the new gauge into the compressor boss until snugly-hand tight, and then turn if just further enough to orient the air gauge face to where you can best see it.

No need to over-tighten, as the pipe dope will seal the threads if they are screwed in just past hand tight and if you tighten too much, the gauge may break.

Plug in your compressor (after you have closed the tank drain valve) and away you go. You might want to put some soapy water around where the gauge threads go into the compressor just to satisfy you that the gauge fitting is not leaking.

Done!

Tank gauge right - regulator gauge left

The reason there are (should be) two gauges on a typical air compressor is to provide the user with two important bits of information.

One of those gauges will be a tank gauge. Its purpose is to display the pressure of the compressed air inside the tank. If you monitor this air gauge, you will see that it stops reading a higher pressure when the compressor stops (at the cut out pressure level). Then, as you use air for your air tool, the tank gauge pressure reading will drop. When the pressure in the tank reaches the compressor cut in pressure level, the compressor should start. Once again, the pressure reading on the tank gauge will start to rise, until the tank is full of pressure to the cut out pressure level of the compressor.

The other gauge, and this one is normally closer to the discharge coupler from the compressor, is the regulator gauge. In some cases, this gauge is plumbed directly onto the regulator. On other compressors, this gauge might be in a panel, and be plumbed a bit of distance away from the actual regulator itself. No matter how it is plumbed, what this gauge will display is the pressure setting that the regulator is set for at that moment.

If, for example, the regulator is set at 50 PSI, the regulator gauge will display that setting. The regulator setting, and the corresponding reading on the regulator gauge will normally not change as air is being used.

That setting is the pressure level that is being allowed to flow downstream to the air tools. Regardless of the tank pressure, whether the tank be at 120 PSI or 80 PSI, the regulator will only allow 50 PSI to flow past it.

That is unless the tool is using more compressed air than can be generated by the compressor, in which case, once the pressure in the tank falls below the regulator setting, both the tank gauge and regulator gauge displays will decrease until, ultimately, you have used all the air the compressor has, and then both gauges will read zero PSI.

Questions? Just ASK!

If you are using high demand air tools and have plumbed them with an air hose or air hoses, after you have done your work, water vapor in the compressed air in those lines could condense out. The next time you connect that air line to an air tool, along with the first burst of compressed air, could come a slug of water. Not good for the air tool if it gets to it, for sure.

In one of their compressor manuals, Campbell Hausfeld suggests, and I thank them for the suggestion, that when the work is done for the day, if you can hang the air hose connector down (the connector is open all the time) if there is any water in the air line, it will drain out while hanging.

Not a crisis if you do not do this, but certainly a potential plus if you do.