HW Cylinder (vented): Combination cylinder or not?

[Ch_152]

Hi. I live in a split level 2 bed flat, there's a big CWS tank and a vented HW cylinder in the spare room upstairs. These feed the taps in the upstairs bathroom and hot water to the kitchen via a Salamander pump.

Shower is an electric unit run off the mains, which has very low flow (at best around 4 l/m, which is usable, but sometimes as low as 2.5 at which point the shower will sometimes cut off).

Primary goals are better shower pressure, and would love to remove the CWS.

I was thinking of doing the following, do you see any issues with it?
- Install pump to mains (maybe with a small storage tank) and supply mains water to all outlets
- Remove CWS tank
- Install an indirect combination cylinder like this: https://www.plumbnation.co.uk/indirect-combination-cylinders-399-0000
- Replace dual pump with single head pump for the hot water
- Replace electric shower with a mixer shower running from mains and stored HW

The much cheaper option is of course to just run a pumped electric shower from the CWS, but I'd really like to remove the CWS tank if possible as it takes up so much space.


Thanks


Chris

 

[SpecialK]

Do you have any access to direct mains pressure water? What is the flow and pressure? If its low, find out why?

Appreciate you say electric shower runs off the mains but I am unsure if you mean the electric mains or water...

 

[Madrab]

Easiest approach would be to keep the CWSC - either run a dual whole house pump and use a mixer shower. Or replace the current shower with a power shower and run it from the CWSC and Cylinder

If you want to remove the CWSC then yes, you would need to go mains. The pumped combi cylinder could be used but you need to match that with the mains and pumping both that way is getting awfully complicated

Pumped mains will give you approx 12l/min @ ~1.5bar - what is the current available mains dynamic flow and pressure?

 

[Ch_152]

Do you have any access to direct mains pressure water? What is the flow and pressure? If its low, find out why?

Appreciate you say electric shower runs off the mains but I am unsure if you mean the electric mains or water...

Easiest approach would be to keep the CWSC - either run a dual whole house pump and use a mixer shower. Or replace the current shower with a power shower and run it from the CWSC and Cylinder

If you want to remove the CWSC then yes, you would need to go mains. The pumped combi cylinder could be used but you need to match that with the mains and pumping both that way is getting awfully complicated

Pumped mains will give you approx 12l/min @ ~1.5bar - what is the current available mains dynamic flow and pressure?

Thanks both.

Been through the whole rigmarole with Thames water. They measured outside the block of flats, and got a decent flow (~25 l/m) but fairly low pressure (around 1.7 bar).

By the time it's up to my kitchen (2nd floor of the building) it's around 5-6 l/m at 0.7 - 1 bar (static - not sure how to measure dynamic?). Once up at the shower on the floor above (via some very convoluted pipework) it's considerably less.


@Madrab, that sounds fair - I may be over complicating things. I understand all of the flats in the building suffer with the same problem and use either whole house pumps from stored cold & hot water (which is what I have to my taps and bath), or thermostatic power showers from the CWSC and cylinder.

Unfortunately, I've only got 1 supply (mains) running to the shower at the moment, so would require a fair amount of destructive work in the bathroom to implement either of the above which was why I was thinking the electric shower with built-in pump might be an easier option but would provide a tangible upgrade.

Seems I may be asking too much to get rid of the CWS altogether.

 

[Madrab]

electric shower with built-in pump might be an easier option but would provide a tangible upgrade.

That suffers from the same problem that your current electric shower does - that being the fact that the shower has to restrict the flow to allow it to heat the cold water up to the desired set temp, flow will still be very low, the level will be dependent on the rating of the shower and the temp of the cold water. Being pumped just means that it's an electric shower that can be fed from a cistern rather than the mains.

With that level of mains then to get the best outcome you are probably going to have to stick with the CWSC and cylinder - pump both supplies (nice strong 2bar ST monsoon pump) and then go to a conventional shower. I appreciate the level of upheaval running another supply is a pain but TBH that will probably be better in the long run.

Only major consideration is pump noise when using the toilet at night but that could be worked around.

To test dynamic readings - connect the gauge to an outlet and then run at least 2 others for pressure - at the same time measure 60secs into a bucket and measure volume of water, to arrive at dynamic flow.

 

[Ch_152]

That suffers from the same problem that your current electric shower does - that being the fact that the shower has to restrict the flow to allow it to heat the cold water up to the desired set temp, flow will still be very low, the level will be dependent on the rating of the shower and the temp of the cold water. Being pumped just means that it's an electric shower that can be fed from a cistern rather than the mains.

With that level of mains then to get the best outcome you are probably going to have to stick with the CWSC and cylinder - pump both supplies (nice strong 2bar ST monsoon pump) and then go to a conventional shower. I appreciate the level of upheaval running another supply is a pain but TBH that will probably be better in the long run.

Only major consideration is pump noise when using the toilet at night but that could be worked around.

To test dynamic readings - connect the gauge to an outlet and then run at least 2 others for pressure - at the same time measure 60secs into a bucket and measure volume of water, to arrive at dynamic flow.

Very fair point.

It might be that the existing electric shower is just plain broken (I only bought the place recently and don't know when it was installed), but as it stands when I have the electric shower (one of these) on the "eco" power mode (4.5 kW), the flow rate coming out of it is terrible (must be around 2 l/m). However, when on the "high" power mode (full 9.0 kW), the flow rate is much better, but even running on the lowest temperature setting it is often still too hot to stand under. Although some mornings it's fine, others it's not.

I'm not quite sure why that is, but had thought it might at least be less susceptible to variance in incoming water temperature or flow from Thames Water's supply?

I think you're very right though in that, ultimately, the most sensible solution probably involves running both CWSC and HW cylinder to the shower on a whole house pump (or to a power shower).

For context, the reason I'd initially asked the question initially is that I want to change the hot water cylinder (I'm on Economy 7, but it only has a single supply at the top and is too small) and wasn't sure whether my thoughts on the combined cylinder (removing the CWS entirely) were viable. As it appears they're not, I'll not buy a combined unit!