Hello,

I have done a bit of reading on this site and others, however would like to put my questions in one place and hopefully someone can set me straight.
Thanks in advance.

We just purchased a 1978 house that has a new low pressure hot water cylinder. These are the details from the building report. "Peter Cocks Ltd, 2009, 180L Low Pressure Cylinder".
I can not remember the setup in the house exactly. We dont take possession for another month.
The hot water cylinder is located on the ground floor, and the shower is on the 2nd floor. The ground floor is concrete floor, and the 2nd floor is also concrete. The shower pressure is rather poor. It has those 'Topless' shower fittings. The show head is one of those typical topless ones with the black knob on it, and the mixer from memory is one that rotates 360 degrees (sorry I cant visualise it). We will no doubt change these to a new mixer and shower head on a rail (the appropriate type for the pressure obviously).

Basically I just want to collect information to make an informed decision when we move in and determine what we want to change.

Since the hot water cylinder is new, I hope there is scope to increase the pipe above the roof and then crank the valve up a bit, else install one of those pressure releif valves which I have read on here about, however I am not sure if they are suitable.
The house is in Invercargill - so cold in winter... Since its concrete floor, I assume the only option for that pressue relief valve is above the roof?, but since its cold here in winter will it freeze up and maybe the cylinder go - kaboom...?

I am not sure what the options are or what is best.
I am happy to get a plumber over to have a look and give a recommendation, however any input people can give here will let me be better informed for when they do come.

Kind Regards
J

Linkback: https://www.plumbers.nz/q-and-a-hot-water-cylinders/44/water-pressure-few-questions/590/

Hi Wana Go,

Sounds like you got yourself a very interesting home.

I agree with you consulting a plumber before taking any action as any advise given can be wrong without having seen the site first.

If a wetback is connected to the HWC directly (not via a heat exchanger),then you CANT install a valve this would be very dangerous and must remain open vented. Extending the pipe would increase the pressure in the system but it would also increase the pressure in the tank. In total it should not increase the recommended pressure rating provided by the manufacturer.

This would also apply if no wetback was connected and you installed a valve on the vent. The valve rating plus your total vent length would equal the total amount of pressure and your right, they could freeze. so not recommended.

keeping it simple is the best way to go. Get a mainspressure HWC with a wetback coil or buy propper low pressure mixers e.g felton mix.

I hope the underfloor is not connected to the HWC, lol 

Plumber

Hi J,

Most low pressure HWC are rated to 800 KPA max. so using a 7.6 KPA would be ok. Maybe all you need to do is increase the pressure on the pressure reducing valve? Have you checked where the water level is at the moment? 1.5 meters does make a difference.

In regards to your plumbing, if the cold pressure is stronger then the hot water pressure then you have an unequal system. That way you know all your cold water pipe is already on mains pressure so usually taps other then shower mixers should be fine. Replacing the HWC could be anywhere between 2500 - 3500 depending on size and location. Most plumbers that replace Topless shower mixers simply cut a larger hole, install a different mixer and then install a larger cover-up plate, can be chrome or simply white. Very common..

plumber