Mixing 22mm and 15mm in a pumped system (whole house)

[Ch_152]

Hi.

I have a property with a traditional gravity-fed system, with bathroom taps running off an old salamander pump with 22mm pipe.

The electric shower runs from mains and pressure/flow is abysmal (we’re talking less than 3 l/m and something around 0.2 bar). I was hoping to upgrade the pump (which is noisy) to an ST Monsoon and also have this feed the shower. Before anyone asks, I've done all possible checks on the mains plumbing, had Thames Water out etc. It's 1.6 bar at ground floor (so TW are happy) and the split-level flat is 2nd/3rd.

The shower is run off 15mm pipe (which runs through the cupboard that the pump is in). I’m trying to work out if that is likely to be a big problem? Especially if the taps are 22 and the shower is 15? There’s potential to make this join the shower piping in the bathroom itself, as close to the shower as possible, so it could only be a couple of meters vertical into the back of the shower that would be 15mm.

I can’t afford to pull the bathroom apart to change the pipe to the shower so if it’s not viable then it seems I’d need to have a separate pump (like ST Showermate which appears to have 15mm connections) for the shower? But having 2 separate pumps (and, I guess, needing two separate feeds from the CWS - not sure how/where they’d split?) is not preferred. Not to mention I still want to replace the existing noisy pump...


Thanks

 

[terryplumb]

Instantaneous electric showers performance are not great at the best of times and 3 to 5 litres per minute of flow during winter months are about all you can expect.
How did you measure 0.2 bar of pressure at the electric shower ?

 

[Ch_152]

Instantaneous electric showers performance are not great at the best of times and 3 to 5 litres per minute of flow during winter months are about all you can expect.
How did you measure 0.2 bar of pressure at the electric shower ?

Fair enough. I mean, really, the pressure is a big part of the problem. It's barely enough to rinse soap off!

As for the 0.2, good question. It wasn't measured - I think someone said it must be around that on the basis of it being ~0.7 at the kitchen tap downstairs, so 5m or so of drop off. So not accurate, but it is definitely not higher than 0.7 bar.


Are there other options which don't involve pulling the bathroom apart (e.g requiring a hot feed for a thermostatic mixer)?

 

[terryplumb]

If you turn your electric shower to fully cold settings ,what is the flow like then ? Let it run water into a container for one full minute on that setting. Then measure how many litres of water it gave. That will tell us the maximum flow rate from your shower . Make sure no other cold taps are running whilst you do it.
Also tell us the shower make ,model and kilowatt rating ( 8.5kw for instance)

 

[Ch_152]

If you turn your electric shower to fully cold settings ,what is the flow like then ? Let it run water into a container for one full minute on that setting. Then measure how many litres of water it gave. That will tell us the maximum flow rate from your shower . Make sure no other cold taps are running whilst you do it.
Also tell us the shower make ,model and kilowatt rating ( 8.5kw for instance)

Fully cold, measured just now, ~5.5l/m. When turned on to a normal shower temperature it was around 3.3 l/m. Noting this is in the middle of the day.

During the peak morning hours the flow is quite a lot lower. A test I did a few weeks back was around 2.4l/m when taken in the morning.

The shower is https://www.mirashowers.co.uk/showers/electric-showers/mira-sport-max-with-airboost-90kw/


Thanks

 

[terryplumb]

There would be no point whatsoever in connecting a pump to that shower. If there is enough pressure to give you 5 litres per minute flow rate the heating elements should at least give you some hot water ,maybe not hot enough for you though. I suspect one of the heating elements may have failed.
if you remove the shower head and do the same test from just the hose, do you get the same flow rates ?

 

[Ch_152]

There would be no point whatsoever in connecting a pump to that shower. If there is enough pressure to give you 5 litres per minute flow rate the heating elements should at least give you some hot water ,maybe not hot enough for you though. I suspect one of the heating elements may have failed.
if you remove the shower head and do the same test from just the hose, do you get the same flow rates ?

The water gets plenty hot, absolutely scalding on the "high" mode. Even when turned down all the way.

Same flows with the shower head off and just the hose. I will add that the pressure has been so bad in the morning at times that the shower won't even turn on.

Everyone on the upper floors of the block suffers from bad water pressure. I understand most have pumps of some sort or showers with built-in pumps, but nobody is giving me the details of their plumbing.


What would be your suggested alternative? Given the very changeable mains pressure I am leaning towards have the shower fed from the CWS, but not sure if that can that be done or not considering the 15mm pipe?

 

[terryplumb]

The water gets plenty hot, absolutely scalding on the "high" mode. Even when turned down all the way.

I am confused ,if it gets plenty hot, and you get 5 litres a minute........?
Turning what down ?
If you have a hot water cylinder and cold water storage cistern ,pumping both hot and cold to a Thermostatic shower would undoubtedly give you better showering / stronger flow than any electric shower.

 

[Ch_152]

I am confused ,if it gets plenty hot, and you get 5 litres a minute........?
Turning what down ?
If you have a hot water cylinder and cold water storage cistern ,pumping both hot and cold to a Thermostatic shower would undoubtedly give you better showering / stronger flow than any electric shower.

Sorry wasn't clear, the shower has 3 heating power settings (high, eco, low). By turning down I meant with the power on high and the temperature control turned right down (which increases the flow out of the unit (while decreasing the temperature, obviously)).

It does 5 litres a minute with it cold. When the heat is turned up to a normal temp for showering, the flow decreases. To around 2 to 3 l/m during the daytime, quite a bit less during the morning, and at fairly abysmal pressure at any time. I'm not the oldest chap, but have had a few showers in my time (plenty electric), and it is most definitely amongst the worst I have ever used.

I thought a pumped thermostatic was probably the best solution for pressure etc. but I can't afford the works required for that (and won't be able to for some time). Also, I currently use the shower over the bath (off the Salamander pump) for showering as it's significantly better than the actual shower cubicle and I run out of hot water by the end of the day. So I'd end up needing to put the immersion on during the daytime, which is expensive on an Economy 7 tariff. More expensive than just using the electric shower.

Didn't realise it was going to be quite such a nightmare when I bought the place...

 

[terryplumb]

How old is your Mira ?
Does the airboost function work ?
Have you checked its filter for cleanliness ?
Is the hose and showerhead the original parts ?
The hose should have a small part inserted in each end ,they are not the same as each other ,they must go in the correct ends, are they present and in good clean condition ?
I suspect your Mira isn't performing as it should ,even with your pressure issue I would expect a better performance than what you outline. At 5 litres per minute your heating elements should give you a fair temperature. Maybe they are scaled up.

 

[Ch_152]

How old is your Mira ?
Does the airboost function work ?
Have you checked its filter for cleanliness ?
Is the hose and showerhead the original parts ?
The hose should have a small part inserted in each end ,they are not the same as each other ,they must go in the correct ends, are they present and in good clean condition ?
I suspect your Mira isn't performing as it should ,even with your pressure issue I would expect a better performance than what you outline. At 5 litres per minute your heating elements should give you a fair temperature. Maybe they are scaled up.

I have no idea how old, it was installed before I bought the property. I am pretty sure the bathroom was done fairly recently before the property was sold though - it all looked pretty new when I moved in (at the start of the year).

As far as I know the shower is all original and the diffuser thing is the right way round in the hose and all looks very clean. I couldn't see a filter anywhere? I opened up and there was nothing internal that looked either inspectable/cleanable or damaged in anyway.

Airboost works, it makes a reasonable difference but can't hide the fact that there just isn't a lot of water coming out to rinse off with.

The water here isn't really that hard, so I don't think it's likely to be scaled up.

Appreciate you taking the time to reply today, thanks.

 

[terryplumb]

Is the water pipe that supplies the shower accessible and in close proximity to the shower ? Is there a water isolation valve on shower supply pipe ?
I am wondering if fitting a shower power booster may improve its performance ,cost around £120, might be worth a punt.

 

[Ch_152]

Is the water pipe that supplies the shower accessible and in close proximity to the shower ? Is there a water isolation valve on shower supply pipe ?
I am wondering if fitting a shower power booster may improve its performance ,cost around £120, might be worth a punt.

Just checked this morning at around 7:45 (so a bit more "peak" time).

Cold: 4.4lm
Normal shower temp: 2.75 l/m

It would be a squeeze, but possibly could fit in the space where the pipes run behind the toilet before going up to the shower itself. Assume you mean an inline thing like this: https://www.bes.co.uk/in-line-automatic-shower-power-booster-sp2b-22904/ ?

But, back to the original question, if I'm thinking of replacing the pump that serves the rest of the bathroom anyway because it's noisy, is there not a possibility to put the shower on that pump (subject to the 15mm pipe not being an issue)?

 

[terryplumb]

Does pump only currently operate on hot water ,or cold from tank as well ?
You can't supply electric shower with pumped hot water. A powerful pump to electric shower would defeat the object ,as water would run through far too fast to pick up the heat. The shower power one is quite weak and really just boosts the flow.

 

[Ch_152]

Does pump only currently operate on hot water ,or cold from tank as well ?
You can't supply electric shower with pumped hot water. A powerful pump to electric shower would defeat the object ,as water would run through far too fast to pick up the heat. The shower power one is quite weak and really just boosts the flow.

Current pump does hot and cold water to taps and shower over bath.

I did just talk to Stuart Turner and they've said that I wouldn't be able to run a twin pump to the shower as running only one side of the pump for long periods of time could damage it.

So it'd have to be a separate pump for the shower, and a pump for the rest of the system. Or a cold pump doing shower and all taps, and a separate hot pump. Either way, 2 pumps which I'd hoped to avoid.


What you say does make sense. The problem with the shower power booster is that I don't have any power outlets in or near the bathroom so would require electrician for that also increasing the cost quite significantly.

I guess another option being to install an electric shower with a built-in pump?! Or continue showering on my knees in the bath while I reset my budget expectations.


Cheers