Hi there, I'm assuming you have a low pressure system at home.
Low pressure systems affect the hot water on showers the most, depending on if its a balanced or unbalanced setup. . There are a few ways you can increase your pressure depending on your situation.

1) Replace the low pressure system with a mains pressure system. (This option is obviously a costly one.)
2) Increase the pressure on your Pressure Reducing Feed Valve very often called a NEFA valve. But WARNING if you increase it to much it will start dumping water up on the roof or through the Pressure/Vacuum Relief Valve. You will find the valve close to the hot water cylinder. It looks like a UFO. Very often they are also located under the Hot Water Cylinder - that's if there is access under the house. (If you have no Idea what your doing please call a plumber...)
3) You might have the wrong gear installed in your shower, that means if the shower head you have installed is a mains pressure one then that could be the cause of your problem. This is something we come across very often. If thats the case all you need to do is install a low pressure shower head or spray.

Again there could be multiple reasons as to why your shower pressure is low. Including a blockage or damaged washer and so on.. I hope this helps and keep in mind that a brief visit by a registered plumber will give you an accurate assessment of the problem. 

Hi Dynamac,

Personally I would not recommend installing the pump to increase the pressure, you would be surprised how many of those we actually have to pull out while having to listen to a very disappointed costumer..

you can increase the height of the vent pipe this will add about 10KPA/per meter, check the pressure rating on your HWC (Its on the sticker) normally this should not be an issue at all and will not damage your HWC. The other option is installing a Pressure relief (vacuum relief valve) on the end of the vent pipe (looks better then a 5 meter vent) usually a 7.6m. Just crank up the pressure on your Ajax valve and watch the relief valve, if it starts dripping turn it back (do this when your water is at its hotest). This method does help increase your pressure slightly.

Otherwise google Hotwatercylinder, many offer a conversion from low to high pressure for under $2400.

hope that helps

Hi Dynamac,

Can you please post manufacture and Model number.

In regards to the pressure relief the 7.6m are equivalent to about 80 KPA. This is expressed as the amount of allowable pressure in the (complete) system including the vent. So when the pressure exceeds 7.6m it will relief. If your water pressure is already at 50 or 60 Kpa then you should not install the valve because it would add 75 KPA to your existing pressure, keep in mind that you are only allowed to have 75 KPA in total, if it exceeds that, you might damage your HWC.

cheers

Spoke to a tech friend @ Rheem, he doesn't recommend adding pressure to your Alpha. Due to age, doing so could cause the tank to leak. Unfortunately you will have to achieve more pressure by either going Mains or installing tapware that copes better with 75 KPA or less. Sorry