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Which shower pumps are suitable for 2 shower homes?

March 14, 2016

When fitting a new bathroom, you might be tempted to devote all your attention to picking out your shiny new shower, but choosing the right shower pumps to handle the extra water demand is just as essential.

The type of pump required depends on a number of factors, including the type of showers chosen, the flow rate of the shower heads, the capacity of the pipework used and whether or not you intend to use both showers at once.

Negative or Positive Shower Pumps?

Shower pumps are divided into negative and positivevarieties. Which kind you need depends on the location of your water cistern and the shower. Bear in mind that shower pumps should be installed in the airing cupboard, as opposed to the loft, to rule out the possibility of the pump freezing.

Negative pumps generate suction to move the water from the tanks to your showers, so they are best used when the shower pump will be located above, or at the same level, as the cold water tank.

Positive pumps, on the other hand, rely on gravity alone to fire up the pump’s impellers (small rotating propellers), which then push the water supply to the shower. Because of the use of gravity to draw the water down, this kind of pump needs a minimum head of one metre between the base of the water storage tank and the shower head.

Single or Twin Impellers?

Another thing you will notice as you look for a shower pump is the distinction between single- or twin-impeller pumps.

Single-impeller pumps can only supply either hot or cold water, as the pump only has one blade which drives the water to the shower mixer. If your water supply is generally balanced and your cold water pressure is not too high, then a single-impeller pump on the hot water supply will be sufficient for a good mix of hot and cold water at the shower head.

If your water supply is poorly balanced, as it often is in urban areas, then you should invest in a twin-impeller shower pump. This will work to balance the supply to the shower of hot and cold water. Without this, your hot supply could be swamped by high-pressure cold water, preventing your shower from getting hot enough. Some brands, such as Grundfos pumps, also offer booster pumps to help manage your water pressure. If you have cats that need to be bathed regularly, it is best that you get a twin impeller, as having a consistent water temperature is important for successful bathing based on reading from this site.

Other Considerations

If you decide to use large shower heads, then you will need a greater flow, making a larger pump necessary. Using one pump to supply two showers can lead to a reduction in pressure when both are used simultaneously, but provided the pump is the correct size, sufficient flow can be ensured. Two bar pumps may be sufficient if you’re not going to use both showers at once, but if you are, a three bar pump is a must.

Regarding piping, the necessary size of the supply pipe is dictated by the connection size of the pump. A shower pump with 15mm couplers requires 15mm pipe, and so on. The flow should not be restricted, especially on the supply end of the pump, so ensure you fit full-bore shower valves to isolate the pump.

An optimal two-shower set-up would use a three bar twin-impeller pump with 22mm feeds from both the hot and cold water tanks. If the showers are located at different ends of your house, then split the feed pipes into 15mm to the different showers directly after the pump for the best performance. If the showers are near each other, then 22mm piping with a split nearer the showers may be more practical.

Installing your pump is another thing that needs to be done correctly for optimum performance. If you are still unsure about which pump would be best for you, get in touch and a member of our knowledgeable staff will be pleased to help.