Steam cabin, shower pump and 15mm pipework woes

[niallcook]

Hi all. Am getting conflicting advice from pump manufacturers so thought I would test the experience of the people who do this for a living.

I am installing a steam shower cabin which requires a hot and cold supply of between 2 and 3 bar and a flow rate of at least 7.5 litres/minute. Per the manufacturer's instructions, I'm planning to feed the steam generator separately from the mains cold so the pump will just be serving the main shower assembly (hand shower, monsoon overhead shower and 6 body jets). The pump will be positioned around 2.5m below the header tank and about 0.5m below the bottom of the hot water cylinder (and 2m below the top of the shower cabin).

I already have a dedicated cold feed from the header tank from the previous shower (in 15mm) and can connect into the hot feed as it enters the bathroom (15mm or 22mm) and before it branches off to the bath and two basins. I have 2 x 15mm pipes running under the floorboards from the pump location to the shower (about 2.5 metres away).

The problem I have is that the pumps I'm being recommended have 22mm connections whereas most of my pipework on both inlet and outlet side is 15mm.

Is it acceptable to take the pipework up from 15mm to 22mm before the pump inlet, and then back down from 22mm to 15mm on the outlet side?

Or would it be better to try and find a pump with 15mm connections? If so, can anyone recommend one for my purposes?

If I can at all help it, I'd rather not have to redo all the pipework in 22mm.

Thanks.

 

[ecowarm]

I would have two dedicated supplies in 22mm

 

[niallcook]

I was afraid you might say that. So is a dedicated 15mm feed from the header tank a complete no-no then? What about the outlet side? It's going to have to go to 15mm at some point as that's what the steam cabin requires. Thanks.

 

[ecowarm]

Its up to you, but its a MINIMUM of 7.5l/m so I would take 22mm as far as possible

 

[niallcook]

Before I go working out how to change all the pipework, what do people think about using a Stuart Turner Showermate U2.6 Twin Universal pump in this situation? Should provide adequate pressure and connects to 15mm inlets/outlets, no?

Any pitfalls to consider? If it's of any help, the old thermostatic mixer valve that both the hot and cold supplies connected to was pretty powerful (without a pump).

 

[niallcook]

One final thought having just been and checked all pipework. As I have a 22mm feed from the hot and can tee off before it goes on to the bath and basins, and a 22mm cold mains running past the shower location, could I just pump the hot and then put the pumped hot and mains cold into a pressure equalising valve that then feeds the shower? Would avoid having to re-do the existing 15mm cold feed in 22mm.

 

[ecowarm]

Independent supplies, not teed from bath/ basin

 

[niallcook]

So I cannot pump a 22mm hot feed, even if it's the first branch off the pipework that comes direct from the HWC?

 

[ecowarm]

Instructions page 2

 

[niallcook]

OK, so following advice here I'm now looking at the least resistance (for me and the water) method of providing dedicated 22mm supplies to a pump suitable for my needs (Salamander recommend their ESP 100 CPV Twin and ST recommend their Monsoon Universal 3 bar twin).

The current pipework is a bit like this:



The 15mm cold on the left is the existing dedicated feed to the previous shower. The top one of the two horizontal hot runs feeds a basin downstairs and the other feeds the bathroom where the new shower will be (including the bath and basin, before running downstairs to the kitchen sink). The CWST is pretty much directly above this.

I think I have two options for siting the pump: either with the HWC (although for space reasons it cannot go on the floor, so would end up above the top of the HWC; or in the bathroom where the shower will be (about 4 metres away, and lower than the bottom of the HWC, properly enclosed and safely connected by an electrician, etc.).

In both cases, I understand that I would need an Essex flange cutting into the HWC to provide the dedicated hot for the pump. I will also need to replace some (and perhaps all) of the existing 15mm CWST feed with 22mm. I can also take the bath, basin and kitchen hot supply off the top horizontal feed, essential turning the lower feed into a dedicated feed for the shower (which already runs into the position I want it). Here's my thinking:

Pump in HWC cupboard:



Pump in bathroom:



So the question is where the best place for the pump is. Specifically:

1. If I put it in with the HWC and put an anti-gravity loop on with the Essex flange, running 22mm to the inlets of the pump, can I then use the existing 15mm cold on the outlet side from pump to shower?

2. Are there any particular 'gotchas' when siting a pump above the HWC? It would still be below the CWST.

3. Do these diagrams look right?

For me, it's the trade off between having to replace the full run of 15mm cold with 22mm and have the pump further away from the supply, and the additional work involved when siting the pump above the HWC.

Any advice, comments, questions, etc. very welcome.

 

[ecowarm]

Go for Picture 3

 

[niallcook]

Thanks for the recommendation. Can you help me understand why this is a better option than siting the pump above the HWC?

 

[ecowarm]

It is to reduce the risk of air getting into the pump or pipework causing airocks

 

[niallcook]

OK, but I thought that's what the anti-gravity loop does. Both Salamander and ST show this as an acceptable configuration.

If I could site the pump on the floor of the HWC cupboard would that make it a better option than locating it in the bathroom?

 

[PlumbBobBob]

that would be my choice

 

[niallcook]

Thanks. So let's assume I can find a way to put the pump on the floor of the HWC cupboard. Would I be OK to keep the existing 15mm pipework on the outlet side of the pump to feed the cold water to the shower or am I likely to get a load of pressure loss along the way?

 

[PlumbBobBob]

you should be fine using the existing 15mm pipework, just limit the amount of elbows used if at all possible because every elbow adds the equilivent of 0.5m to the run.

 

[niallcook]

you should be fine using the existing 15mm pipework, just limit the amount of elbows used if at all possible because every elbow adds the equilivent of 0.5m to the run.

Excellent. That should save a bit of upheaval then. I assume it won't matter if the hot run from pump to shower is in 22mm, reducing down to 15mm further on than the cold?

 

[ecowarm]

so the pump will just be serving the main shower assembly (hand shower, monsoon overhead shower and 6 body jets)

Quote taken from first post Steve, so you think 15mm is ok?

 

[PlumbBobBob]

so the pump will just be serving the main shower assembly (hand shower, monsoon overhead shower and 6 body jets)

Quote taken from first post Steve, so you think 15mm is ok?

i'd forgotten that didn't reread the whole thread lol. in that case feed would have to be in 22mm the whole way otherwise you won't get full benefit from your shower. apologies for misinforming .you

 

[wheeto]

It is to reduce the risk of air getting into the pump or pipework causing airocks

I'm not a domestic plumbing expert, but generally the risk with air in hydraulic pumps direct impeller damage, often indistinguishable from that caused by cavitation.

 

[niallcook]

i'd forgotten that didn't reread the whole thread lol. in that case feed would have to be in 22mm the whole way otherwise you won't get full benefit from your shower. apologies for misinforming .you

For what it's worth, I can't have them all going at once but only switch between them. Anyway, have decided the best bet is to run dedicated 22mm pipework all the way from the CWST and HWC to the location in the bathroom where I'd originally decided to have the pump, and be done with it (I hope). From pump to shower (2m) will use 15mm as it has to drop down for the shower connections anyway.

Of the pumps I've been recommended, does anyone have a favourite?

• Salamander ESP 100 CPV Twin
• Salamander Force 30 TU
• Stuart Turner Monsoon 3.0 Bar Universal