Frequently Asked Questions

The following questions are deemed to be the most popular ones asked by customers installing Mira products.

1- What is the supply pipe centre distance of the surface mounted Mira Excel, Combiforce & Gem 88?
The Mira Excel thermostatic surface mounted mixer has variable inlet pipe centres between 150 - 155mm.
The Mira Combiforce surface mounted mixer has inlet pipe centres at 153mm.
The Mira Gem 88 surface mounted mixer has variable inlet pipe centres between 149 – 154mm.

2- On which plumbing systems systems can I use:
a) The Mira Excel
b) The Mira Combiforce 415
c) The Mira Gem 88

a) The Mira Excel can be used for either low pressure, or high pressure systems
min maintained pressure 0.1 bar
max maintained pressure 5.0 bar
max static pressure 10 bar

b) The Mira Combiforce 415 is designed to be used on ‘high pressure systems’, (for example; use on fully modulating combination boilers)
min maintained pressure 1.0 bar
max maintained pressure 5.0 bar
max static pressure 10 bar

c) The Mira Gem 88 can be used for either low pressure, or high pressure systems but is NOT Suitable for use with Instantaneous Water Heaters / Combination Boilers.
Min maintained pressure 0.1 bar
max maintained pressure 5.0 bar
max static pressure 10 bar

3- After installation of a Mira Excel the water flow from the shower outlet seems very poor. What could be the causes?
The Mira Excel will deliver an adequate shower at 0.1 bar pressure (1 metre head). There are five possible reasons for poor flow.
1) The system pipe work must be flushed before connection of Excel (See current Water Regulations). If not the filters fitted within the Excel may become blocked and require cleaning or replacement.
2) The Mira Excel works best when complimented by Mira shower fittings, where the two are matched in terms of flow and pressure. To this end the Mira Logic shower fittings, supplied with the Mira Excel, have two sets of differently sized rubber, rub clean, spray plates. By fitting the set that makes best use of the pressure a satisfying shower can be obtained.
3) Ensure the spray plate holes are clear, and the shower hose is not twisted or blocked.
4) Head of water below minimum required. Raise the cistern or fit a pump such as the Mira Enduro.
5) The isolating valve/valves to the shower partially closed. Check they are fully open.

4- Can any Mira mixer showers work on high inlet cold pressure (cold mains) & low inlet hot pressure (hot gravity).
Mira mixer showers are designed for use with relatively equal inlet pressures from the same source. They can be used on systems
a)with equal high pressures: eg. Unvented or Gas instantaneous heater systems, or
b) equal low pressures: eg: Gravity or Pumped systems.

5- What is the minimum head of water required for the Mira Event ‘XS’ range of ‘All in One’ power showers?
The Mira Event ‘XS’ range of ‘All in One’ power showers is a product which has the pump and mixing valve in one box, only requires a minimum distance of 80mm from the base of the cold water cistern to the top of the Mira Event ‘XS’ case. This is to ensure there is enough ‘gravity fed water’, to prime the internal pump. This vertical distance will need to be increased dependent on how far the product is away, from the stored hot and cold water supply.

6- If a Mira Enduro or Enhance is installed, why is it that on some occasions a pulsed on/off operation occurs when the shower control is turned off, or the pump operates momentarily when a tap not on the pumped system is operated?
The most common reason for this ‘shunting’ is due to small air locks, or pockets of air, in the system. These will cause water movement through the pump by compression of the air. This momentarily lifts the flow switch causing the pump to operate.
To remedy these problems ensure the hot water connection is made in accordance with Mira Showers recommendations. If the outlet pipe work from the pump is prone to air-locking fit float type automatic air vents at a high point in the pipe work. Additionally there is available, as a spare part from Mira, a check valve that fits in the pump outlet, which will stop this nuisance operation.
Mira have a publication ‘A Guide to Domestic Pumped Shower Systems’ available from Mira Customer Services.

7- Is there an electric shower suitable for use in local authority or healthcare sectors, as most electric showers appear to be non-thermostatic?
YES. The Mira Advance ATL is the first thermostatic electric shower, (controlling to +/- 1 degree centigrade) available.
It incorporates push button control for flow & on/off control plus the ATL ‘Flex’ variant has an extended temperature control lever for easier grip. A maximum temperature setting can currently be set to ensure the outlet temperature does not exceed 43 degrees centigrade. See the Flexible Showering section of the website.

8- What size fuse / Mcb’s are required for the Mira Sport instantaneous electric range when installed on a 240v Electrical supply?
The Mira Sport 7.5kW requires a 35 Amp supply fuse / mcb, the 9.0kW shower require a 40 Amp supply fuse / mcb and the 9.8kW and 10.8kW showers require a 45 Amp supply fuse / mcb.
Mira have a publication ‘A Guide to Instantaneous Electric Shower Installations’ available from Mira Customer Services.

9- What is the minimum cable size required for Mira instantaneous electric showers?
To minimise voltage drop, and thereby maximise shower performance, the minimum cable size required must not be less than 6mm. All Mira electric showers will accommodate up to 10mm, the Mira Advance & Sport ‘Max’ will accept up to 16mm. Use the shortest possible cable route from the consumer unit to the appliance. Reference must be made to BS7671 (previously IEE regulations) to determine cable size. Mira have a publication ‘A Guide to Instantaneous Electric Shower Installations’ available from Mira Customer Services.

10- If a Mira Elite ST, pumped instantaneous shower is installed on mains water pressure, will its internal pump produce a better flow rate than a non pumped electric shower of the same kW rating?
Do not connect a Mira Elite ST to a mains water supply, as product damage will occur and Water Regulations will be contravened.
The Mira Elite ST is designed to be gravity fed from a cold water storage cistern. The Mira Elite ST is not a power shower and a higher flow rate will not be achieved if installed on mains pressure.
A ‘power shower’ is one where stored hot and cold water is pumped via a mixing valve.

2 - What is the benefit of a 'riser leg'?
The riser leg, or number of legs are fitted to the underside, which allows the installer to adjust and correctly level the tray by rotating the legs on a screw thread.

3 - I have heard that it is important to level a shower tray that is to be used with an enclosure. How 'level' do I need to get the tray?
When levelling a tray the spirit level must be placed on the flat raised area around the recessed tray bed. The recessed tray bed slopes towards the 'waste', that is, the outlet pipe.
The degree with which the tray needs to be level depends upon the type of enclosure to be fitted, the more level the tray, the easier it will be to fit the enclosure.
A fully framed enclosure is more tolerant of a tray that is not entirely level.
The maximum 'out of level tolerance', for say a 900 square tray fitted with a fully framed enclosure is around 4mm.
For a part framed enclosure the maximum 'out of level tolerance', for say a 900 square tray, is less at a maximum of 2.5mm.
With a good quality spirit level this accuracy is easy to achieve.
The installation and adjustment of an enclosure will be much easier if the tray is level.

4 - Which type of 'waste water trap' should I choose?
There are two main types of 'waste traps', top access and bottom access.
A top access waste allows the fitting to be serviced, that is, cleaned out from above, so that access to the underside of the shower tray is not needed.
A bottom access waste is similar to the type used in hand basins, where there is a 'cup' that can be unscrewed from below to clean out any debris that has become trapped.

5 - How do I repair a small chip in a Flight shower tray?
The 'acrylic' can be repaired by using a purpose designed repair kit, this is available with full instructions from Anglo Adhesives of Leicester and they can be contacted on 01664 480866.

6 - Why are some trays very heavy?
The heavy trays are made from a resin and stone mixture, which provided a stable and 'non flexing' tray.
In addition, there are trays made from pressed steel, then glazed, stainless steel, fibreglass, to name but a few.
The heaviest of all are manufactured from fireclay, the same type of material that is used to manufacture the 'Belfast' sinks.

7 - How do I repair a small chip in a Resinstone shower tray?
The 'gelcoat' can be repaired by using a purpose designed repair kit, available from Kohler Mira Customer Services, in Cheltenham. This contains gloves, fine emery paper, instructions and the repair solutions needed.