Rainhead replacement

[morqthana]

I need to put a new rainhead on my shower (an Aqualisa Midas).

Is the thread on the end of the pipe going to be a standard one, which any head will fit? If not, what should I measure to find out what it is?

Also, would appreciate suggestions for makes to look at - one must have is no "chrome plated" plastic. I don't mind it having a plastic part, as long as it's 'honest', but if it looks like polished stainless steel I want it to be polished stainless steel.

Lastly, it runs off a combi, so I guess I don't need a head meant for "high pressure", but does it mean I shouldn't get one, or would it not matter?

 

[cross thread]

Most area standard 1/2 inch bsp thread.majority are plastic.

 

[CountryFan]

Lastly, it runs off a combi, so I guess I don't need a head meant for "high pressure", but does it mean I shouldn't get one, or would it not matter?

It’s usually stipulated as to the types of systems thy can be fitted to, most notably are low pressure and electric showers.

 

[Madrab]

As suggested, it all depends on the type you get. The flat plate type heads, which are usually the ones that are all steel, would normally require a high flow mains pressure shower and supply given the flat design and narrow waterways in the head to maintain a decent flow. With an Aqualisa Midas and a combi then flow and pressure shouldn't be an issue as they need =>1bar.

The thicker type heads are more universal and can be used on lower pressure/flow systems but more of them do tend to be plastic.

So it all really comes down to what type you want. Just get a direct replacement from Aqualisa?

 

[Justin Passing]

Pressure and flow are different, obviously, so quoting one tells you nothing about the other.
A combi will give you more flow than the ~4l/min you get from an electric shower and the pressure from both can be deemed high, but a combi's output on both measures will be totally inadequate for a big high flow rain head. A 4.5 bar twin pump fills anything at 40l/min.
Your mains could be as low as say 1 bar (or less upstairs) and your combi could provide say 10l/min, depending on the combi, the time of day and the time of year.
You need the specs for the head - good luck getting those.

"Low pressure" just means water will come out down to something like 0.2 bar (2 metres head) or whatever they quote.
The pressure AT the shower head is what they mean, not something most plumbers would think to measure.

 

[morqthana]

The pressure AT the shower head is what they mean, not something most plumbers would think to measure.

And presumably not easy to measure.

Flow rate (cold/hot/mixed) I could easily measure.

As suggested, it all depends on the type you get. The flat plate type heads, which are usually the ones that are all steel, would normally require a high flow mains pressure shower and supply given the flat design and narrow waterways in the head to maintain a decent flow. With an Aqualisa Midas and a combi then flow and pressure shouldn't be an issue as they need =>1bar.

Makers spec isn't much use - it just says 1 - 10bar, but the existing Midas one works fine.

The thicker type heads are more universal and can be used on lower pressure/flow systems but more of them do tend to be plastic.

So it all really comes down to what type you want. Just get a direct replacement from Aqualisa?

That would be the path of least resistance. I didn't know it was plastic, but now I do, and I'm disgruntled by that. And I'd like to get a slightly larger one if I could - Grohe do a 310 (80% bigger).

Mind you - it's astounding just how big a 255mm head is in practice...

 

[Madrab]

I can safely say that the rain showers in the picture are not 255mm, the perspective is all wrong. I have a Mira Activate with a ceiling fed rain shower head @ 250mm and it's no where near as big as it looks like in pic 1. To give an idea, 300mm is the size of a normal ruler and a typical forearm from the elbow is anywhere from 14" (360mm)

 

[foxhole]

Has a couple of the chromed plastic fail quickly, the limescale build up burst the seam on the head .

 

[denso13]

I can safely say that the rain showers in the picture are not 255mm, the perspective is all wrong. I have a Mira Activate with a ceiling fed rain shower head @ 250mm and it's no where near as big as it looks like in pic 1. To give an idea, 300mm is the size of a normal ruler and a typical forearm from the elbow is anywhere from 14" (360mm)

I think that's the point of the smiley face, it's a silly picture which isn't real.

 

[Madrab]

Missed the smiley!

 

[Justin Passing]

And presumably not easy to measure.

Simple -- T piece, pressure gauge.

An average 28kW combi won't work well with a big rainhead.. Imagine splitting the flow from your current 100mm head up evenly to cover the area at 9x.. It'll probably widdle, unless the holes are tiny.
I remember someone complaining that she had to move about to catch the drips, when her stored water + big pump was replaced with a 35kW combi.
I've had a decent shower under a big head from a storage combi, until the store was used up and the flow practically stopped.
Give the mfr a ring.

 

[Madrab]

An average 28kW combi won't work well with a big rainhead

Not sure where that's coming from? IME combi's can cope with a rain head shower without a problem, as long as the mains pressure and flow is up to it. A typical 28kw combi can output say ~12L/min @ 35deg rise, add in the cold mix then ~18L/Min is more than enough to supply most IMO. The rain shower head will deliver what is supplied and I think most people would be more than happy with an 18L/Min shower.

Of course it's not going to be the same as an unvented @3 bar mains or a 3bar pumped OV @ >25L/Min but that's comparing apples and oranges. It also comes down to what is considered to be a large rainhead shower. I've fitted 12" rain shower heads onto showers fed by combi's numerous times without an issue.

 

[Rodders53]

I can affirm that Grohe rainheads are plastic... at least in the Euphoria 260 3-spray form that we have... the 310mm may only have single spray setting.

Check/consider the weight of any replacement head on the riser bar and its fixings - especially if you can find an all-metal construction one!

 

[Justin Passing]

Not sure where that's coming from?

Experience. I won't have fitted anything like the number you have, though.
Unless the holes are tiny (which I haven't seen) , I find it's just pathetic. 300mm dia is 9x the area of a 100mm, so try it - turn your tap down to get you 2l/min out of your 100mm head and that's what the flow will feel like.
On an electric shower (total about 4l/min) they put pinholes in the head, so the flow is fast enough to feel ok. A head for a combi-fed shower would be awful so they don't provide them.
Opinion on "OK" I guess - but that's mine!
No it doesn't compare with a good water supply ("hotel" grade) - that's what the big heads are made for, rather than combis, is the obvious answer.
Maybe there are big heads with smaller holes than I've seen.

I've got a head somewhere which was fine on a big pump but hopeless (imo) on a combi - I'll post a pic if I can find it. It's not that big.
The "water saving" heads which combine air in the flow can feel better - good for the actual flow.

~12L/min @ 35deg rise, add in the cold mix then ~18L/Min

That would be 15l/min with winter incoming mains at 10° (national UK shallow groundwater temp). We all shower at close to 38°.

I checked the temp with AI. It misheard, saying the groundwater temp in Maine gets to 4°C!

 

[morqthana]

Imagine splitting the flow from your current 100mm head up evenly to cover the area at 9x.. It'll probably widdle, unless the holes are tiny.

Mine is 280mm. 36kW Combi. Works absolutely fine.