Hot water supply options/upgrades

benson1980

Hi all,

Making headway with getting my bathroom install done and it seems timely to have a look at our hot water pressure issues. Situation presently is that we have an old gravity fed system. Large tank in the loft (and small one for CH) and vented cylinder in airing cupboard. Two shower rooms upstairs where pressure is poor. Downstairs shower is good, so I guess the typical gravity fed issues. The conventional boiler we have is fine. I'm not necessarily minded to go the combi route.

I understand that the two main options are to install a pump, or go for unvented cylinder. I'm leaning towards the latter because:
- potentially better pressure?
- our existing cylinder is old, possibly not large enough for family of 4 (we do tend to run out occasionally, but, I understand increasing pressure will mean using up the water quicker so probably much of a muchness in that regard)
- option to move it out of the airing cupboard, potentially. It is a bit noisy
- the tank in the loft is a bit irritating and pipework up there is messy. Old, sludge build up, and it is right in front of the access door (previous owner split the loft into one loft room and the other half is...the loft. Tank in middle of house so right by the door). It would be good to tidy it all up and just have one cylinder.

Next steps are to get some heating engineers round and quotes, but would be good to get some advice in advance of this obviously, from any knowledgeable people on here. Anyone with experience of doing similar? Also at the back of my mind is whether 2k ish outlay (or potentially more?) is the way to go in terms of investing in a conventional heating system, but I guess this is a bit of a crystal ball type scenario....I'm not aware of any other options really, presently. The only other thing I could find are heat batteries which don't really seem to be mainstream.

Thanks.

BUFF

1st thing is what is your existing mains supply like (pressure & flow rate)?

Increasing pressure needn't increase usage if you use the right fittings (btw if you go mains pressure then some of your existing taps may need replaced or restricted). In fact many of the most eco friendly taps/shower heads will be high pressure.

Pumps do have their uses but usually come with noise (how much depends upon what type, quality, how/where installed etc.), require electrics & are an extra potential point of failure.

benson1980

BUFF said:

1st thing is what is your existing mains supply like (pressure & flow rate)?

Increasing pressure needn't increase usage if you use the right fittings (btw if you go mains pressure then some of your existing taps may need replaced or restricted). In fact many of the most eco friendly taps/shower heads will be high pressure.

Pumps do have their uses but usually come with noise (how much depends upon what type, quality, how/where installed etc.), require electrics & are an extra potential point of failure.

Thanks- I haven’t measured the mains pressure as such but it seems very good from the kitchen tap. As in much more powerful than the hot. I don’t really understand the cold supply upstairs and why it has been done as it has, but it is basically fed by the big tank rather than the mains? Therefore it’s basically the same flow rate as the hot.

noise is a good point and key factor as well- as in the less noise the better as our airing cupboard is right by one of the bedrooms and is a bit noisy. 

Bendy_House

As said above, an unvented cylinder will be powered by the mains, so having this checked for P and F is the first step. Your cold mains kitchen tap might seem good, but what comes out there will have to supply EVERYTHING, H and C, if you go 'unvented'. There are ways to boost this, from upgrading the mains supply pipe (if this is the issue), to fitting a mains booster tank, but that's all extra expense/complexity.

A warning issue here is that you mentioned that you occasionally 'run out of water', so that suggests that the CWS doesn't refill from the mains as quickly as it should. So, your cold kitchen tap might APPEAR to be good, but by the time the cold mains has reached the loft, it could well be compromised.

Yes, your existing vented/gravity system is dependent on 'head', so upstairs will always be more lacking unless you fit pumps. These would only really be needed for the upstairs showers, and could be fitted - relatively well sound-isolated - in the loft, so would only be 'noisy' for short periods, so perhaps not an issue?

Yes, currently both the H and C will likely be supplied from the loft so that they are 'balanced' as they come out the showers and taps. So that's normal.

The 'running out of water' issue could be sorted by either fitting a larger CWS, adding a second one, or by having its mains FILL rate increased by a wee 12lpm £200 pump. Yes, we are getting quite 'pumpy' now, but hey...

A quick test you can do yourself at your kitchen cold; open fully into a bucket for 10 seconds, measure no. of litres, and 'times' by 6 to get lpm.

I'd personally lose the small F&E tank when you change your boiler -  go sealed, system boiler imo.

Any potential for raising the heights of the (new) CWS in the loft as you move them out of the way?

If going unvented hot cylinder, where would it live - where the current tank is, or also in the loft?

Options:

1) keep current system, add shower pumps or possibly increase height of CWS. Increase size of CWS or add mains refill pump. If you can get more CWS head, then possibly low pressure shower mixers supplied by their own dedicated pipes might suffice without needing pumps.

2) go unvented, fit new hot cylinder in loft if you like. Depends on mains supply.

3) go unvented, boosted with mains booster tank such as Challis, Stuart-Turner or Grundfos. This will deffo give you everything you want.

Basically, first explore if you can boost what you currently have; CAN the gravity supply be boosted by raising the CWS? CAN the incoming mains be boosted with a new mains supply pipe?

What systems do your neighb's have, IF they are in similar (size, storey and number of bathrooms/showers) types of houses?

benson1980

Bendy_House said:

As said above, an unvented cylinder will be powered by the mains, so having this checked for P and F is the first step. Your cold mains kitchen tap might seem good, but what comes out there will have to supply EVERYTHING, H and C, if you go 'unvented'. There are ways to boost this, from upgrading the mains supply pipe (if this is the issue), to fitting a mains booster tank, but that's all extra expense/complexity.

A warning issue here is that you mentioned that you occasionally 'run out of water', so that suggests that the CWS doesn't refill from the mains as quickly as it should. So, your cold kitchen tap might APPEAR to be good, but by the time the cold mains has reached the loft, it could well be compromised.

Yes, your existing vented/gravity system is dependent on 'head', so upstairs will always be more lacking unless you fit pumps. These would only really be needed for the upstairs showers, and could be fitted - relatively well sound-isolated - in the loft, so would only be 'noisy' for short periods, so perhaps not an issue?

Yes, currently both the H and C will likely be supplied from the loft so that they are 'balanced' as they come out the showers and taps. So that's normal.

The 'running out of water' issue could be sorted by either fitting a larger CWS, adding a second one, or by having its mains FILL rate increased by a wee 12lpm £200 pump. Yes, we are getting quite 'pumpy' now, but hey...

A quick test you can do yourself at your kitchen cold; open fully into a bucket for 10 seconds, measure no. of litres, and 'times' by 6 to get lpm.

I'd personally lose the small F&E tank when you change your boiler -  go sealed, system boiler imo.

Any potential for raising the heights of the (new) CWS in the loft as you move them out of the way?

If going unvented hot cylinder, where would it live - where the current tank is, or also in the loft?

Options:

1) keep current system, add shower pumps or possibly increase height of CWS. Increase size of CWS or add mains refill pump. If you can get more CWS head, then possibly low pressure shower mixers supplied by their own dedicated pipes might suffice without needing pumps.

2) go unvented, fit new hot cylinder in loft if you like. Depends on mains supply.

3) go unvented, boosted with mains booster tank such as Challis, Stuart-Turner or Grundfos. This will deffo give you everything you want.

Basically, first explore if you can boost what you currently have; CAN the gravity supply be boosted by raising the CWS? CAN the incoming mains be boosted with a new mains supply pipe?

What systems do your neighb's have, IF they are in similar (size, storey and number of bathrooms/showers) types of houses?

Ok thank you. Some good pointers there. There is no means of raising the storage tank presently, so that is one option off the list but will have a look at the others.

Bendy_House

Basically, don't entertain 'mains' unvented unless you are certain you have enough flow and pressure. OR, you are prepared to also fit a pumped booster tank.

Your kitchen tap flow test will be good first indication, tho' not always accurate. It should show the minimum flow available, and I'd be looking for comfortably over 20lpm before considering it further. And this would need to be backed with a decent pressure - 3 bar-ish plus. 

There are a few good low pressure shower mixers, say by Mira (Exel range), that will make the best of a gravity supply, especially if given dedicated feeds from the H&C supplies.

Grundfos make a variation of their CH circulating pump which is used to boost gravity systems and has a built-in flow switch. These are ideal for providing a very useful boost (around 0.75bar pressure) without being 'stupid', and are very quiet in operation. These WILL give you a cracking shower when used with a low-pressure thermo shower mixer.