15mm/22mm compression reducers, just before the pump ?

[Reynardine]

How can my plumber install a powerful 3.5 bar twin shower pump under my bath when all my bathroom pipework is in 15mm copper pipes? I won't be doing the work but I still want to be informed and understand the issues.

I've checked my CW cistern and HW cylinder. All my pipework from is in 15mm diameter copper piping which extends all the way to the terminal fittings ( i.e. shower / taps ) in my bathroom. This is a problem because the powerful shower pumps I have in mind ( e.g. over 1.5 bar ) all expect pipework to be in 22mm.

My original workaround plan was to use 15mm/22mm compression reducers, just before the pump, in order to change the pipework up to the required diameter. However, I have rung a pump manufacturers customer services for technical guidance and this practice is not allowed, or at least it is strongly frowned upon.

So my options are:

a) keep all pipework in 15mm and settle for a weaker 1.0 bar twin pump
b) buy a powerful 3.0 bar twin pump but replace all 15mm pipework between CWS, HWC and pump with 22mm pipework.
c) keep all pipework in 15mm, buy a powerful pump, and install compression reducers "back to front" to increase the pipework diameter from 15mm up to 22mm just before the pump.

Any guidance welcome.

 

[doitall]

Your plumber will know what is best.

Fitting the pump by the cylinder and replacing all the pipework, is what he should be saying.

Then he will have calculated the size of the storage tank and suggested that it isn't large enough, and you need at least a 100 gallon tank.

But then again he may just fit what you want and take the money.

 

[Richard C]

Your plumber will know what is best.

Unfortunately not always the case; many seem to have their head up there arse when it comes to designing a pumped shower system so it will work properly.

Fitting the pump by the cylinder and replacing all the pipework, is what he should be saying.

Absolutely agree & If it were me, I’d be replacing all the pipe work with 22mm, right up to the mixer valve & only installing full bore lever valves where isolation is required; the pumps no good under the bath in fact if more than 5m from the hws cylinder, you may be very dissapointed!

Then he will have calculated the size of the storage tank and suggested that it isn't large enough, and you need at least a 100 gallon tank.

The minimum you need is 50 gallon; 100 gallon would be nice but probably not necessary unless you have 2 or more showers that could be used at the same time or take really long showers. Your hws cylinder should also be a minimum 140 litres.

But then again he may just fit what you want and take the money.

Many of them will do that anyway, make a pig’s ear of it & still not fit what you want!

Seriously, I would take some time to read through the archive posts on shower pumps & study one or two of the manufacturer’s design & installation guides. Problems with bad installation come up on here all too often & the mistakes can be monotonously the same each time; I can’t imaging you want to be posting on here with the same problems in a few weeks time.

 

[Reynardine]

Ok thanks for the guidance - I've read around a bit more now.

Measuring horizontally, my bath is just four feet away from my HW cylinder so in terms of pump power I'm going to keep the new pump located under the bath and hope this does not compromise performance.

I haven't yet measured the capacities of my HWC or CWS but my plumber tells me my CWS is "twinned" with another CWS so I'm hopeful about my cold supply being sufficient. I'm going to measure these capacities just in case.

Stuart Turner don't seem to make any pumps with a 15mm inlet - they all expect 22mm pipework so I've ruled these out. Thankfully Salamander make a 2.1 bar twin pump that only requires 15mm pipework so I'm going to go with this.

I must do something as my flow rates are pathetically low at the moment at around 2 litres / minute (hot) and 3 litres / minute (cold). [ mains flow rate is around 8 litres / minute ]

 

[dextrous]

Would have thought the plumber would be installing a flange into the cylinder and a dedicated feed from the CWSV anyway all in 22mm.

 

[Richard C]

Would have thought the plumber would be installing a flange into the cylinder and a dedicated feed from the CWSV anyway all in 22mm.

Definitely the way to go. I would think seriously about installing a pump using 15mm supplies. The cylinder may be only 4ft away but it's the length/route of the pipe runs in 15mm that will reduce flow rate to the pump considerably; you can reduce to 15mm on the outlets but, as I said previously, I would run 22mm all the way to the shower mixer. You need to ensure the system can meet the minimum 1 litre/min un pumped flow rate or the pump will not work properly.