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How Does a Pressure Reducing Valve Work?

It’s quite rare for people to worry about high water pressure. However, when it does happen, it could cause a lot of problems. If you fail to address the issue or protect your system using the right piece of equipment, you could end up spending thousands of dollars on repairs or replacement. It could also result in damaged appliances such as laundry machine and dishwashers. 

Several things can cause high water pressure. For example, supplying companies have to ensure that all of their customers get enough water supply. Hence, they sometimes have to use high pressure to pump the water, especially in areas dotted with high-rise buildings. Another factor that could cause your problem is thermal expansion, a common issue triggered by water heater use. 

It’s not possible for the supplying company to reduce the water pressure, so your only option is to have it adjusted using a pressure reducing valve. 

What is a pressure reducing valve?

Essentially, a plumber installs a water pressure reducing valve near your water meter to control the hydraulic pressure coming from the main line. It’s crucial to double check the type of pressure reducing valve you will install to ensure that they work well with your system.Here are the main three types you can find in the market: 

  • Direct-acting – It’s the simplest and most economical type which works well with both convoluted bellows and a flat diaphragm. This type of PRV works best for low to moderate water flow. 
  • Externally piloted – This type of PRV comes with double diaphragms, which allows for higher capacity and increased sensitivity to water flow and pressure changes. It also offers you the flexibility to make use of different pilot valve types such as soleniod, air-loaded, pressure, temperature or combinations. 
  • Internally piloted – It incorporates a main and pilot valve and uses inlet pressure to open the valves. Compared to the direct-acting type, it has a higher capacity and accuracy. It also senses pressure internally, so you don’t need to add an externally installed sensing line. 

To know which among the three would best fit your system, you should consult with a professional plumber. They can provide you with the necessary details to help you decide.

How does a PRV work?

Now that you’re acquainted with what a pressure reducing valve is plus its three main types, let’s take a closer look at how it works. 

A typical PRV is designed to work even in the harshest environment. Regardless of pressure or upstream flow fluctuations, a PRV ensures a steady downstream pressure. It does this with the help of its major components such as the valve body, pilot regulator, and control filter. Here’s how each part works: 

  • Valve body – It stabilises the returning water flow while regulating the pressure.
  • Pilot regulator – Think of it as the “brain” of the valve body. Basically, it determines the water flow coming in and out of the chamber.
  • Control filter – Located inside the valve system, this filter helps you minimise damage because of accumulated debris coming in from the main line.

The system works by opening or closing the valves depending on the available upstream flow. So, for example, if the pressure in the upstream line is high, the pilot regulator drops the plunger, triggering the valve to gradually open. Consequently, if the upstream flow is low, the pilot slightly lifts the plunger, causing the valve to slightly close.

This all happens continuously, even if you don’t use water. It’s a straightforward process that happens quite fast. With the right pressure reducing valve in place, you can ensure that your household or commercial space gets enough water and protect your system from all kinds of pressure-induced mishaps. 

Shop for a Pressure Reducing Valve Today!

You’d be surprised by the usefulness of a tiny piece of item like a pressure reducing valve. With it in place, you can avoid nightmarish situations such as burst pipes, damaged water consumer lines and defective appliances. The best part is that they don’t cost a lot of money.     

If you live in an area here in New Zealand where the water pressure is too high such as Christchurch, you will definitely need a PRV installed. If you’re not certain about the water pressure of the supply line, you may find it useful to check it yourself using a water pressure gauge. You can also stay on the look out for common signs of high water pressure such as:

  • Banging noise in the pipes
  • Low water supply in your hot water cylinder
  • Unreasonably high water bill
  • Unexplained noise coming from your dishwashers or washing machine

Looking for a water pressure reducing valve for your plumbing system? Find the perfect one here at Hotwater Cylinders. You can choose from more than hundreds of items in our product catalogue. If you need more information about a product, don’t hesitate to get in touch with us.

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Hot Water Cylinder Trays Are Now Mandatory

IMPORTANT NOTICE: Safe trays are now compulsory with all new internal hot water cylinder installations, as per G12/AS1 clause 5.2.3 of the New Zealand building code.”

The above notice is what you will find on most newly sold (Image of a Rheem) hot water cylinders. Last year one of our blog posts discussed whether or not you need a cylinder tray. At the time the blog discussed a faulty product which resulted in flooding and insurance claim. In that particular instance the damage was minimal and covered by the manufacturer. Can you imagine the yearly claims when thousands of hot water cylinders are installed without hot water cylinder trays?important_notice

You can take a big guess on who would have lobbied the idea and pressed to get this incorporated into recent New Zealand building code G12 amendments. This standard sets a legal guideline on how a hot water cylinder may and may not be installed.

WHO BENEFITS?

Looking across the ditch, our Australian friends have had this requirement (regulation) as part of their compliance documents (e.g standard AS/NZS 3500) since 1996 but for some reason it never made it into the New Zealand building code, until now.

AS/NZS 3500 is also an acceptable standard in NZ which begs the question, why bother with two sets of standards in the first place?

Previously, accidental discharge control was optional unless a potential risk of water damage to another property existed, which in most cases only really applied to multi-story situations. Although control was considered “good practice” the homeowner could “opt out” to achieve savings on the installation. Or the plumber would keep it on the quite “to be competitive” and win a job against more expensive quotes that included the installation of a hot water cylinder tray.

Before the change, manufacturers such as Rheem have stated in installation instructions that a safe tray must be fitted, meaning plumbers should have already been recommending, quoting and installing hot water cylinder trays.

Now that this law has come into effect, ignorance is no longer bliss and benefits are relative to:

> The manufacturer knowing that installers can made responsible for water damage if the standard is not followed.

> The homeowner, knowing that any potential leaks are controlled while they are sleeping.

> The insurance, knowing they can legally peruse compensation on behalf of the homeowner.

Additional benefits also include:

  • Level playing field when plumbers are pricing jobs.
  • Prevention being the best protection.

NOTE: Plumbers and homeowners should ensure the installation complies with the updated standard to avoid any costs associated with non-compliance or resultant damage from water discharging from a hot water cylinder. 

SOME CHALLENGES AND CONSIDERATIONSunderbench_cylinder_on tray

Progress is always accompanied with challenges and challenges are accompanied with questions.

Some legalities are still undefined and It is not clear on whether a cylinder try must be installed on replacement hot water cylinders as well as newly installed hot water cylinders. When a “repair” or “like for like replacement” takes place, the building act allows one to maintain the current state of affairs. For example, although tempering valves are required by law, a plumber does not have to install a new one when replacing an existing old or damaged hot water cylinder that never had a tempering valve to begin with. Its good practice but not a legal requirement. He can just go ahead and maintain the existing setup treating the installation as a “like for like” situation.

But then this principal does not apply to seismic restrains. The DHB is yet to comment on this and we will update the blog once we know more.

Because compliance is relative and no job is like another, you want to be safe and ask the right questions before committing to any installation. Its always best to make an educated decision rather than deal with the unwanted consequences of ignorance.

ALTERNATIVES WHEN IT GETS TO EXPEN$IVE!rheem_27_instant_gas_water_heater

A cylinder tray needs to be connected to an approved point of discharge via a 32mm – 40mm drain. In many cases, for example double story homes the route of this drain becomes a major challenge. Especially when you are talking about cutting walls open or having surface mounted pipework to get the drain out.

If the cost or convenience of having a cylinder tray is not attractive, there are alternatives within the same ballpark in terms of $$$.

 

 

external_hot_water_cylinder

For example Instant water heating. For about the same price of new hot water cylinder + tray you can convert to gas and enjoy the many benefits. We offer LPG and natural gas solutions. Future-proof or expand, your possibilities are limitless.

Alternatively…

Relocate your hot water cylinder to the outside and free up that cupboard space. In external situations, no cylinder tray is required and the costs are about the same as a new internal hot water cylinder + tray.

Most of our customers tend to go for this option when the installation of a cylinder tray becomes too difficult or expensive. Talk to us for more information.

AMENDMENTS IN G12, 

Lets have a look at G12 a bit closer.

You can view the old and newer version (third edition) of G12 by following this link VIEW G12 AMENDMENTS.

Its very interesting to see that they have removed the wording from 6.11.3

a) Safe trays complying with Paragraph 5.2.3 where water could penetrate another household unit within the same building.

Which now reads:

6.11.3 Storage water heaters shall have: a) Safe trays complying with Paragraph 5.2.3

tray insallation

The above relevant paragraphs read as follows:

5.2.3 now reads..

Safe trays Performance E3.3.2: states that; Free water from accidental overflow from sanitary fixtures or sanitary appliances must be disposed of in a way that avoids loss of amenity or damage to household units or other property. An acceptable method of preventing water damage is to locate a safe tray below the water tank (see Figure 4). The safe tray shall incorporate a drain with a minimum diameter of 40 mm. Where the tank overflow discharges into the safe tray, the diameter of the safe tray drain shall be greater than the overflow pipe from the tank and comply with Paragraph 5.2.2.

RELATED PARAGRAPHS

5.2.2 Overflow pipes Water tanks shall have an overflow pipe to discharge any overflow to a visible place within the same property that does not create a nuisance or damage to building elements. The overflow pipe shall be sized so that the discharge capacity is no less than the maximum inlet flow. The outlet of the overflow pipe shall not permit the entry of birds or vermin. Overflow from a WC cistern may discharge internally into a WC pan.

COMMENT: Manufacturers’ literature must be referenced for pressure and flow information on tempering valves and tapware. Outlets (e.g. shower mixers and showerheads) must be appropriate for the available flow and pressure. Note the limitations on lengths and pipe sizes given

6.11 Water heater installation

6.11.1 Water heaters shall be installed in accordance with the manufacturer’s instructions.

6.11.2 Where heating units, sacrificial anodes, thermostats, pipework connections, valves, or other accessories being components of a storage water heater are installed, they shall be accessible for inspection, maintenance and removal.

6.11.3 Storage water heaters shall have: a) Safe trays complying with Paragraph 5.2.3 b) Connections compatible with the pipe material used, and c) Drain pipes (for every storage water heater of more than 45 litres capacity) which: i) have a conveniently located isolating valve, and terminate with a cap or plug suitably located to easily empty the vessel for maintenance, or ii) terminate outside the building with a cap only.
cyl;inder setup

The installation below shows the safety valves discharging into the cylinder plug and waste, which does not comply as one could argue that these pipes are blocking the passageway designed for the control of accidental water which is managed by the safe tray only. NZ Regulations define acceptable methods of discharge which includes safety valve drains.

cylinder_drains_into_tray

 

 

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Low pressure after installing mains pressure?

cylinder_blockageHow would you feel if you just had your low pressure hot water cylinder upgraded with a mains pressure to only get the same low pressure you had before? Not happy, right?!

I thought this story was interesting because it tends to happen very often and we from Hot water cylinders ltd end up getting the phone calls to investigate and repair. In this scenario some cylinder guy replaced the hot water cylinder and forgot to remove the transport thread protection, completing the installation with this inserted into the pipe. After the installation was complete this “bung” found its way to the valve blocking any flow of water. the poor home owner was not sure what to think of it for over 4 weeks and put up with the low pressure thinking it may have been normal until he picked up the phone and made the call.. “Uhm.. excuse me.. if I have a mains pressure cylinder should it be dribbling out of my shower head?”  Well.. NO of course not.

Mistakes made by Noobs are fixed by professionals. Want to learn more bout LP cylinders? Click here for information about low pressure hot water cylinders.

OTHER REASONS YOU MAY HAVE LOW PRESSURE AFTER A MAINS PRESSURE INSTALLATION INCLUDE:

  • The non return valve was installed incorrectly (opposite way in reverse)
  • Debris from the installation found its way to the strainer in the tempering valve blocking flow
  • Transport bungs are not removed
  • The incoming diffuser has accidentally been pushed into the tank causing a blockage
  • Pipework is kinked restricting flow
  • Pipework badly brazed restricting flow
  • Pipework badly crimped restricting flow

Not sure what the issue is? Please give us a ring and we will help you get to the bottom of it!