Surrey Flange - Is it Really Essential

[camel307]

The house I have moved into has 2 MIRA shower pumps to feed 2 separate showers.

I am now looking to install a shower pump as the bathroom pressure (excluding the MIRA shower) is poor! I also don't currently have a bath but will be installing one so want this to fill quickly.

I have considered just fitting a pump under the bath to supply the bathroom just by tapping in to the existing pipe run. However I understand that doing this might activate the pump when I use non bathroom appliances (although it will stop instantly after turning on). However, I have considered fitting a 1 way valve just before the pump input? Has anyone tried this?

I also understand that the 'proper way' to do this is to install a surrey flange and take direct supply to the pump. However, 1 MIRA shower pump (professionally installed prior to me buying house) has been in operation for circa 5 years with NO issues and after reviewing the installation instructions there is absolutely no mention of a surrey flange. I don't understand therefore why an in-line pump requires to be fed from a surrey flange? The MIRA shower pumps work on the same principle and this has not suffered with air blowing up the motor???

Thanks guys

 

[Madrab]

Do not restrict the flow into the pump, it's flow activated.... it's low pressure system as it is and a check valve may affect the pumps operation.

A flange does promote longer pump life by avoiding cavitation (air bubbles being drawn into the impeller), this can cause premature impeller failure and so is there to cover the manufacturers guarantee, if they stipulate a flange then if it's not fitted then it's not covered.

It's a catch all tho, not all cylinders are the same, some create more bubbles, are set hotter etc, therefore a standard hw take off from the top of a cylinder could allow air bubbles to be drawn into the pump, causing the cavitation and prematurely damaging the impeller.

If the primary HW draw off is angled up then this helps to avoid air being drawn in but a flange also allows a dedicated feed to the pump, therefore output on the main HW circuit to the other hot outlets isn't affected, when the pumps running.

 

[camel307]

Great advice Rob.

Makes good sense. Thanks!!!!