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When meeting with numerous washroom companies to discuss their WC products, one of the most common questions brought to the table is, “which are the most economical and environmentally friendly washroom products available?” with a particular focus on BREEAM flow rates and flush volumes.

At Dolphin Solutions, we continuously optimise the features of our washroom products to help our clients achieve their sustainability goals while delivering a budget friendly solution.

Dolphin concealed cisterns are the most popular WC products to specify. Due to innovation efforts, we can confidently say that the improved delayed action inlet valve in our concealed cisterns is the most valuable water saving and economical device in a toilet on the market today.

But first, we need to explain how a typical traditional float valve works and how it wastes water. Then, we can help you understand how the innovative delayed action inlet valve works and how it saves water – and money.

A WC pan with traditional float valve in a concealed cistern

Traditional float valve in a concealed cistern

How does a traditional float valve work?

When the flush plate or lever is activated, the flush valve opens and gravity forces water out of the tank into the toilet bowl.

The traditional float valve (also known as a slow-fill valve) consists of a float attached to an arm, which is connected to the flush valve at the bottom of the tank. When the water level in the tank drops, the float falls with it and the arm opens the water supply allowing water to flow into the tank simultaneously.

When the tank is empty and the flush valve closes, the water level in the tank rises with the new water coming in from the traditional slow-fill valve. As the float rises with the water level, the arm gradually closes the water supply until the flow of water stops.

What is the problem with how a traditional slow-fill valve is designed?

As the float descends, new water flows through the slow-fill valve during a flush and mixes with the water already exiting through the outlet valve. Essentially, the water that flushes into the toilet bowl takes the new water with it until the tank is empty and the flush valve closes.

How is water wasted with a traditional float valve?

The faster the water exits the tank, the faster the traditional float valve descends with the water level, and the faster the water pipe opens to let new water in. Essentially, the water pipe is filling the tank with an open flush valve at the bottom, which is pointless and is how water gets wasted.

Although the traditional float valve pours water into the tank at a slow pace, it essentially tops up the water level as the tank empties. Therefore, even though the tank is draining quickly, the combination of new water flowing into the flushing water firstly prolongs the time it takes for the tank to empty and for the outlet valve to close, and secondly wastes water by taking extra new water with it.

How many litres of water is wasted?

Up to 0,5 litre of water is wasted per flush before the water level gets to the low point where the flush valve closes.

This quantity is astonishing when you start calculating the extra litres of new water going down the drain with the flushed water.

Illustrated drawing of how a delayed action valve in a concealed cistern work

Delayed action valve in a concealed cistern

How is the delayed inlet valve different from a traditional slow-fill valve?

The improved delayed action inlet valve stays closed while the cistern drains when the flush is activated, and it only opens to fill the tank once the tank is empty and the outlet valve has closed.

How does the Dolphin delay action valve work?

The float that opens the delayed action inlet valve has its own reservoir of water. This reservoir empties in a regulated manner, slower than the cistern. As a result, the opening of the inlet valve is effectively delayed until after the outlet valve is closed.

How much water is saved with a delayed inlet valve?

Here is an example to understand just how much water can be saved with a delayed action inlet valve:

There are 1000 occupants in an office building, and each person visits the washroom three times a day (flushing the toilet once per visit), and let’s say the office is occupied for 200 days of the year, taking into consideration hybrid/remote working and bank holidays.


1000 people X 3 flushes daily X 200 days in the office X approximately ½ a litre of water = 300 000 litres of water saved in a year.

If you look at the bigger picture in a scenario like this, you will agree this is an enormous amount of water savings.

How much money does a delayed inlet valve save?

Firstly, the cost of water and sewage services in the United Kingdom can vary depending on several factors, such as the location, the amount of water used, the type of property, and the specific water company that serves the area.

But referring to the 300 000 litres of water savings per year example (according to the above calculation), you can only imagine the significant amount of money you are saving on your utility bill.

Watch our video on how the delayed action inlet valve save water and money.

Doc M commercial washroom with floor mounted toilet pan

Does the delayed action valve affect cleaning out the toilet bowl?

Some may argue that the delayed action inlet valve may prevent adequate water from flushing contents out of the toilet bowl, resulting in insufficient cleaning of the bowl.

The tank design already has an effective flush volume of either 6/3 litres or 4/2.65 litres, which is sufficient to flush out and clean the toilet bowl. Therefore, the delayed action inlet valve does not affect the cleaning of the bowl. Its only purpose is to save the extra water that would typically flow into the tank during the flush process, and it does not add any benefits to the flushing.

Why is this inlet valve special?

Dolphin Solutions’ delayed action inlet valve in a concealed cistern is a more efficient and effective way to manage water usage, making it a special feature for those who are environmentally conscious and want to save on their water bills.

Cost and water saving wall hung WC pan equipped with delayed action inlet valve

Benefits of the delayed inlet valve for a toilet

The two significant benefits of a delayed action inlet valve are:

  • Environmental impact
    Water is a finite resource, and many regions around the world are facing water scarcity issues. By reducing water consumption with a delayed action inlet valve, we can all play a part in conserving this precious resource and promoting sustainability.
  • Cost savings
    The most obvious benefit of reducing water consumption is the cost savings on water bills. By choosing water saving washroom products that include a device like the delayed action inlet valve, businesses can significantly reduce their monthly water bills, which can add up to significant savings over time.
  • The Dolphin delayed action inlet valve in our concealed cisterns combined with our WC pans is the most valuable return on investment and the ultimate washroom solution if conserving water, saving costs on utility bills, and keeping within your budget is essential for your washroom project.

If you would like us to demonstrate how our delayed action inlet valve for a concealed cistern operates, please reach out to us using the contact form below or call us. We will be happy to answer any more questions you have.

Get ready for our washroom specialists to present the most innovative water and cost saving washroom solution yet.

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