Home Water Systems: The Ultimate Guide

There are two ways to enjoy the benefits of showering.  One is to install a shower above a bath and the other is to install a self-contained shower unit.  Overbath showers do offer some of the advantages of showering.  They typically use less water than a bath, making them better for the environment and more economical, moreover they can be used more quickly than a bath (since there is no need to wait for a shower to fill) plus they avoid the need to “sit in your own dirt”.

Weak Pressure Bath Shower

Even the best over-bath units, however, are unable to match the performance of a self-contained shower unit.  There are two basic reasons for this.  One is the fact that the water feed is intended to fill a bath and has to be forced up a pipe or tube before it is brought down on the user by gravity.  This means that there are very limited options for controlling pressure, in fact many over-bath showers have none at all.  Another is that the temperature can only be controlled by the taps, which means that it is harder to set precisely and impossible to have pre-set options, whereas showers can be thermostatically controlled.

The final key disadvantage of over-bath showers is the very fact that they are over the bath.  In other words, you still have to step into and out of the bath, which can create difficulties for those with restricted mobility.  This means that there are a number of advantages to installing a separate shower.  What type of shower you can have and how it needs to be fitted will depend on your home water system.  Here we’ll take a look at the most common types of home water system and what they mean in practice when considering installing a shower.

Identifying the water system in your home

The very easiest way to identify what kind of water system you have in your home is to check to paperwork which came with your house.  If you didn’t get any or can’t find it, then, if it has been built relatively recently, the builder or your utility company may be able to tell you.  If none of these is possible, then you will need to check your home for clues

Q1. Do you have a boiler?

The answer to this is almost guaranteed to be yes, but in the unlikely event that the answer is no, then you have a direct link to the cold-water mains.  Your only option here is a basic electric shower.  At this point in time, electric showers are unable to support more advanced options such as massage jets since they are completely dependent on gravity and flow to push water from the source and out of the shower head.

NB: it is both illegal and dangerous to attach any sort of pumping equipment to a mains-fed water system. You will need to install a storage tank to hold the water and pump from here if it needs a boost in pressure

There are a couple of other points to bear in mind when dealing with electric showers.  The first is that water and electricity really do not mix, which means that the necessary cabling has to be installed to a particularly high standard and this, of course, comes at a cost.  The second point is that electric showers are notorious for temperature fluctuations, which means that they really benefit from having a thermostatic control.

As a side note, electric showers can also be a good choice even where other types of shower could be fitted.  For example, if you have a home with a combi-boiler system and want to create an extra bathroom without placing extra demands on your boiler, then an electric shower may be a way to get around the problem.

If the answer is yes.  The next question to ask is:

Q2. Do you have a hot-water storage tank?

If your home has a loft or a dedicated airing cupboard, then these are the places to check to see if you have a water-storage tank.  If your home is too small to have either of these, or you do have these but there is no tank in either of them, then you have a combination or “combi” boiler.  Combi boilers provide both heating and “on demand” hot water.  They have become increasingly popular over recent years, partly because of their overall efficiency and partly because they remove the need to have a separate water-storage tank, which can be a huge advantage in smaller homes.  They can support showers however there are a couple of caveats to bear in mind.

Typical Modern Combi Boiler

Combi boilers tend to be found in smaller homes because their output capability has to be shared by all output points.  This means that if more than one output point is in operation at any given time, then they are essentially competing against each other for the boiler’s resources.  The classic example of this is trying to fill a sink at the same time as someone is having a shower.  In smaller homes, with a limited number of occupants, this issue can generally be managed with a bit of common sense, however with the best will in the world, misunderstandings and miscommunications can occur. This means that using manual mixer showers (which work in essentially the same way as mixer taps in that the user opens them as wide as they want to achieve their preferred temperature) carries the risk of the shower user either suddenly being drenched in cold water or, more seriously, (albeit more rarely), being hit by scalding hot water.  Because of this, it is strongly advisable to opt for a thermostatically-controlled shower.

A thermostatically-controlled shower is one in which the hot and cold water is mixed to a pre-set temperature before it is delivered to the user.  As an added safety feature, if the cold-water supply fails (for example by some flushing a toilet), then the thermostatic device will automatically switch off the hot water to prevent the user from being scalded.  If you are using a thermostatically-controlled shower in a combi-boiler water system, then it is generally strongly recommended to fit a pressure equalizing valve.  Basically the hot and cold feeds tend to have a difference in pressure and unless this pressure is equalized with a PEV it will eventually damage the thermostatic valve.  How long this will take depends on the extent of the pressure difference, which varies with the installation.  You may find that fitting a PEV is a requirement for your warranty to be valid.  In theory, showers fitted to combi-boiler systems can support advanced features such as monsoon jets.  In practice, however, it is, as a minimum, an open question as to whether or not this will actually work in reality due to the limitations on pressure even before other outputs start being used.

If you do have a hot-water storage tank, then your final question is:

Q3 Do you have a cold-water storage tank in your loft?

If the answer is yes then you have what is called a gravity-fed system and if it is no then you have a mains-pressure unvented system.  Both of these systems can support showers, however, as always, there are a few specific points to bear in mind.

Gravity-Fed Water Systems

There is a reason why these systems are also known as “low-pressure” systems.  There is also a reason why cold-water tanks are usually located in the loft and hot-water tanks are usually located in upstairs airing cupboards.  Basically the water is brought down into the house, literally, by the power of gravity and therefore the higher up the water source is located, the longer gravity has to do its work and the greater the level of pressure which can be obtained.  This means that ideally, in a standard two-storey home, a gravity-fed shower would be located on the lower floor.  Of course, in the real world, main bathrooms are often located on the upper floor alongside the bedrooms.  This means that unless there is space, budget and willingness to create a separate downstairs shower room, you may find that your shower has less pressure than you’d like.  Gravity-fed showers are not fed directly from the mains and therefore can use booster pumps, which is good news for those who like to feel the force when they have a shower.  If, however, you want to go all the way with sprays and jets then you may need to look at installing a shower on the ground floor since a booster pump may not be sufficient to support this on an upper floor and if it does it may create an unacceptable level of noise.

On the plus side, gravity-fed showers tend to be the safest showers to use in that they are the least susceptible to changes in pressure and temperature.  Having said that, installing a thermostatically-controlled shower mixer rather than a manual one will make for the greatest possible level of safety and therefore make it possible for the shower to be used safely by the old, the young and those with reduced sensitivity to temperature, such as diabetics.

Mains-Pressure Unvented System

In a lot of ways mains-pressure unvented systems are like combi-boiler systems writ large.  First of all, there is competition between the different households attached to the main water source and secondly there is still competition between individual outputs within any given household.  The former are essentially the responsibility of the local authority and/or utility company, while the latter can generally be managed by cooperative behaviour.  As with combi-boiler systems, however, it can be very helpful to use thermostatically-controlled equipment as a safeguard against temperature fluctuations.  On the plus side, this is probably the absolute best water system for those who want a “full on” shower experience with high-pressure, sprays jets and everything and anything else.  It should even be feasible to install such a system in an upstairs bathroom.

NB: Although it’s highly unlikely to be an issue with mains-pressure unvented systems, it is still both illegal and dangerous to attach any sort of pumping equipment to a mains-fed water system.

Shower Cabin Water Supply Requirements – An infographic by the team at Shower Cabin Water Supply Requirements

Andrew Ellis is the 'hands-on' webmaster, content curator and Captain of the good ship Poshh Living Father of one and master of none. Fitness, health and of course home improvement are Andrew's key areas of expertise. Andrew has worked in many roles, from product designer to purchaser, for spa products, garden furniture and tech. Andrew is a really well-respected voice within these business circles.

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