Second shower has much lower pressure

[smithfield11]

We’ve just bought a new house (new build). The main bathroom shower above the bath is extremely powerful however the rainfall AND handheld shower in the en suite are significantly lower.
They’re both mains fed showers from a new 35kw combi.
I can’t work out why one shower would be so poor when the taps and shower elsewhere are much better in the rest of the house.
Any advice much appreciate, thanks in advance.

 

[John.g]

Do they just feel less powerful at the same showering temperature?, a 35 kw combi will provide a flow rate of 14 LPM with a 35C temperature rise and should give nearly 17 LPM from cold water at 10C (just now) with a showering temperature of 40C. There may be flow restrictors fitted in the en suite showers.

 

[smithfield11]

Do they just feel less powerful at the same showering temperature?, a 35 kw combi will provide a flow rate of 14 LPM with a 35C temperature rise and should give nearly 17 LPM from cold water at 10C (just now) with a showering temperature of 40C. There may be flow restrictors fitted in the en suite showers.

Yes, it's definitely a subjective "feel" however than hand held head on both, when on full power at the same temperature:
- In the ensuite pointed horizontally the hand held head will express water less than 2 feet before it's falling vertically
- In the main bathroom the hand held head will express water the length of the room (8 feet+) without any noticeable dip

I'll need to check re: a flow restrictor but not sure how to do that.

 

[Ben-gee]

Blocked filters in the shower inlets, or partially closed valves?

 

[smithfield11]

Blocked filters in the shower inlets, or partially closed valves?

Ill have a look at how to check this. Just trying to get a feel for if this is likely something fundamental (I.e the boilers crap or the pipes are wrong) or if it’s something wrong with the setup of the shower

thanks for the input

 

[John.g]

Yes, it's definitely a subjective "feel" however than hand held head on both, when on full power at the same temperature:

• In the ensuite pointed horizontally the hand held head will express water less than 2 feet before it's falling vertically
• In the main bathroom the hand held head will express water the length of the room (8 feet+) without any noticeable dip

I'll need to check re: a flow restrictor but not sure how to do that.

There may be different size jets in the heads but one relatively easy test is to measure the flow rate from each by letting it (them) flow into a dish for say exactly 30 secs and measure this with anything suitable and X by 2, it saves a lot of toing and froing.

 

[smithfield11]

There may be different size jets in the heads but one relatively easy test is to measure the flow rate from each by letting it (them) flow into a dish for say exactly 30 secs and measure this with anything suitable and X by 2, it saves a lot of toing and froing.

Thanks, I'll pop back over to the house tomorrow and check this, will come back with the numbers. Out of interest why times by 2?

 

[John.g]

Because you require the flow rate in LPM (litres per minute) and you might get fed up with filling a one lire milk bottle 14 times instead of 7 times.

 

[smithfield11]

Because you require the flow rate in LPM (litres per minute) and you might get fed up with filling a one lire milk bottle 14 times instead of 7 times.

I've been to check flow rate. We have three shower heads:
- one hand held head above the bath (perceived high pressure)
- one rain head in the ensuite (perceived low pressure)
- one hand held head in the ensuite (perceived low pressure)

All feed off the same 35kw combi system.

- Hand held head above the bath: 12.45 LPM
- Rain head in ensuite 6.9 LPM
- Hand held in ensuite 7.95 LPM

So there's a notable difference being caused by something, any further advice much appreciated but it might be "get a plumber in and give him these numbers"

 

[Timmy D]

Can you test the en-suite handheld and rain without the heads?

Can you test the combined hot/cold flow from the en-suite basin?

 

[smithfield11]

Can you test the en-suite handheld and rain without the heads?

Can you test the combined hot/cold flow from the en-suite basin?

looks like you clocked it. Took the rain head off and got the same pressure, but then took the rain head gimble/adapter off and it outputs at 12.5 lpm

I’ve attached a picture as with a bit of trial and error it appears that the small orange piece is the limiting factor. With that in its low. Without it’ll doup to the 12lpm. Is it required?

 

[John.g]

Yes, I would think that's one of the restrictors I mentioned, (except that its a aerator) just replace the shower head without it and see how it goes.
[automerge]1606389439[/automerge]
If you install that restrictor in the shower head above the bath then you will make history by (nearly) being able to run two showers together, especially in the summer, from a 35kw combi boiler.

 

[smithfield11]

Yes, I would think that's one of the restrictors I mentioned, (except that its a aerator) just replace the shower head without it and see how it goes.
[automerge]1606389439[/automerge]
If you install that restrictor in the shower head above the bath then you will make history by (nearly) being able to run two showers together, especially in the summer, from a 35kw combi boiler.

Haha yeah, was thinking getting 12.5lpm of actually hot water from a 35kw combi was pretty good tbh, so didnt want to lose it by not getting it out my main shower.

Thanks for the help

 

[Timmy D]

looks like you clocked it. Took the rain head off and got the same pressure, but then took the rain head gimble/adapter off and it outputs at 12.5 lpm

I’ve attached a picture as with a bit of trial and error it appears that the small orange piece is the limiting factor. With that in its low. Without it’ll doup to the 12lpm. Is it required?

View attachment 46404

Good job buddy. What I expected/wanted to prove.

The aerator, mixes the water with additional air through multiple small holes. This reduces water usage and increases the perceived pressure (water through a smaller opening, increases in velocity).

Glad it’s resolved.

 

[Ben-gee]

The orange insert is a flow limiter, they restrict the flow as the water causes the oring to distort and this blocks some of the holes- so it works at different pressures.
It has been put in to allow the combi to heat the water up sufficiently- however it may not have been needed, as appears to be the case here. It is also an ‘eco’ measure.

 

[John.g]

That's interesting re how they work, I think 6LPM is the Eco aim.

 

[Ben-gee]

Wow they’re pushing it down! My shower has eco setting at about 9lpm - this is achieved by the on off valve and has a button to override it (‘snail trail’ - the same as most showers have on the temperature override).
To be honest 98% of the time it gets used at 9lpm, but I reckon at 6 people would override more often.

But like the ridiculous situation we find ourselves in with wc cisterns needing to be flushed twice at 6l each instead of once at 7/9 litres!

 

[exedon2]

All this is down to part G building regs on new build you have to show that the system will only use 125lts per person per day.
On sustainable development limit is a good deal less
Can assure you the forms are a pain!

 

[Ben-gee]

To actually save water in the real world, not just in an office on a spreadsheet, we need to go back to syphon flushes instead of dump valves - these didn’t used to be allowed in uk afaik.

 

[exedon2]

To actually save water in the real world, not just in an office on a spreadsheet, we need to go back to syphon flushes instead of dump valves - these didn’t used to be allowed in uk afaik.

Could not agree more re flush valves and the whole thing becomes a nonsense when end user can just remove flow restrictions!