Advice re adequate hot water for master bathroom in Loft Conversion

[RockyLeeLee]

Hello, and thanks in advance for reading my essay! I'm hoping to get some unbiased advice on the best way forward.

I'm currently going through a permitted development application for a dormer loft conversion which will create a large master bathroom which will have both a whirlpool bath and a walk in shower - rainfall head and body jets. - Well that was the plan until I started researching upgrading my current heating system and I'm now doubting whether it's going to be worth it, hence my post here.

1950s 3 bed, 1 bath mid terrace house, with a sealed gravity system - cold tank in loft, cylinder and expansion vessel in 1st floor airing cupboard, 20 year old Potterton boiler on the kitchen wall. 6 rads. System currently working fine.

The dream is to create a luxurious bathroom in the loft - I've put up with a tiny bathroom for 20 years and want a bit of luxury while I can still get up the stairs 🙂, so removing the cold tank is required.

On doing my research and based on the fact that although it's only two people in the house, the requirement for water will be high - I'm thinking of 15 minute steaming hot showers with the overhead and jets going at the same time - but only for a couple of times a day, I had decided for an horizontal unvented cylinder in the eaves, with a greenstar 18i system boiler in the same place as the current boiler.

The first plumber pretty much came up with that as a solution and has quoted me for that, however he didn't test the pressure or flow while he was there.

British Gas came out last night and said that the pressure is only 1.5 bar / 15l/pm so can't install an unvented system as it needs to be min 2 bar/20l/pm. He recommended a combi, which I'd already discounted due to the one outlet only issue - ie I wouldn't be able to have jets and shower going at the same time.

If I can't get the bathroom to work how I want it to, there's no point in doing the loft.

Can anyone suggest anything else to look into before I give up on my luxury dream bathroom?

Just to confuse things, the 3rd guy that came this morning tested the outside tap only and said the pressure is great - 4 bar and over 22l/pm as it went up to the max on his gadget. I'm confused....... He recommended a 36i combi boiler.

Any advice/comments would really be appreciated.

Thanks

 

[Last Plumber]

For the plans you have, I would forget combi boilers personally.

The water main will need to be up to the job for an unvented cylinder, as you know.
There seems to be a big difference between BG's figures and the third man's figures (he wasn't called Harry Lime)? That fluctuation could be down to demand and where you are on the supply but the gap seems larger than I would expect.
You would be best to go off the peak time figures. If the main is no good, the only other options to provide the volume you need would more than likely take up too much room and be too commercial for a domestic property.

 

[RockyLeeLee]

For the plans you have, I would forget combi boilers personally.

The water main will need to be up to the job for an unvented cylinder, as you know.
There seems to be a big difference between BG's figures and the third man's figures (he wasn't called Harry Lime)? That fluctuation could be down to demand and where you are on the supply but the gap seems larger than I would expect.
You would be best to go off the peak time figures. If the main is no good, the only other options to provide the volume you need would more than likely take up too much room and be too commercial for a domestic property.

Thanks for taking the time Last Plumber, appreciated.

Thanks for confirming my views on combi boilers, it just seems to be the preferred choice for most plumbers I've contacted. I was pretty confident based on what I'd researched that a combi is just not suitable for multiple outlets, but have had at least 2 plumbers tell me 'it will be fine' or that 'they've got one in their house and it works fine with two showers going at once'. They also give me the 'you're a woman' look so 'just listen to me, I'm an expert!', so I did start to doubt myself!

I've emailed the BG guy and asked him for all his readings. He did the first test for the unvented. Had the outside tap on, the kitchen tap and the bath tap going. Then he did it again for the combi calculation?

He did mention an accumulator (which I see is also mentioned on a similar, recent thread) but that BG couldn't supply/install one. I'm going to be spending upwards of £50k on the conversion, so don't mind spending a bit more for a solution that works. There will be space in the loft that I could sacrifice for an additional tank/thing if it would improve the pressure/flow.

I'm in South East London, but apparently would need to be in Wimbledon to get the pressure I need from the mains (not sure how true that is).

I'm now re-thinking if I can do without the body jets, but a little piece of me died with the dream 🙂

Thanks again.

 

[centralheatking]

Water pressure and volume is at a premium in London, you are right to beware. I really would look at conventional high level intermediate cold water storage..the old fashioned system. Store enough water then you can do what you like. It will build up water overnight ready for the morning onslaught and recover during the day for your return.
centralheatking

 

[Brambles]

You could consider a pumped accumulator - they work very well in North London where the flow rates are around 10 lpm, boosting it to 30 plus lpm. In an ideal situation they should be on the ground floor, with a storage volume of between 200 and 400 litres.

 

[ShaunCorbs]

You could consider a pumped accumulator - they work very well in North London where the flow rates are around 10 lpm, boosting it to 30 plus lpm. In an ideal situation they should be on the ground floor, with a storage volume of between 200 and 400 litres.

that would only give you around 10 mins at 30lpm with the 200l one

 

[Brambles]

True, my preference is 400 litres, but I have a number of customers who are happy with 200 litres. I can only surmise, that their actual shower time is shorter than their perceived shower time !

In cost terms, 400litres verses 200litres is around £500 installed.

The issue (in London) is often available space for the tank

 

[RockyLeeLee]

Water pressure and volume is at a premium in London, you are right to beware. I really would look at conventional high level intermediate cold water storage..the old fashioned system. Store enough water then you can do what you like. It will build up water overnight ready for the morning onslaught and recover during the day for your return.
centralheatking

Thanks for taking the time Centralheatingking, it's appreciated.

Do you mean keep my existing system (upgrading the boiler and cylinder) would be sufficient? It did cross my mind after the BG man left, but then I thought the pressure would be worse as I'd have to put a coffin tank in the eaves, on the same level as the bathroom.

The bath should be fine, I don't mind if it takes a while to fill and I'll probably get an in-line whirlpool heater. But it's the shower that's giving me the headache.

Your suggestion did send me back to google though, a new question - would a shower pump - eg Stuart Thompson Monsoon universal twin 3.0bar, be enough for what I want? It almost seems to easy?

I'd get a bigger cylinder - currently got an Albion CF120 in the airing cupboard and it's been okish for my current set up (20 years old, installed with the Potterton when I moved in) although the water does go cold if another tap gets used, so would want to definitely get rid of that issue at the same time! So if I got a coffin tank cold water in the the loft, a new efficient boiler, a larger vented cylinder in the airing cupboard + the shower pump (assuming somewhere close to the shower in the loft?) strong enough for the jets and shower head together could it work?

Again, any comments and suggestions much appreciated.

Thanks
[automerge]1573170271[/automerge]

You could consider a pumped accumulator - they work very well in North London where the flow rates are around 10 lpm, boosting it to 30 plus lpm. In an ideal situation they should be on the ground floor, with a storage volume of between 200 and 400 litres.

Thanks for responding Brambles, appreciate your input.

I have done a bit of research on these now and as you suggest am thinking I'd probably need 300/400l to get the amount of water for the shower. There would be nowhere to put it on the ground floor. I could potentially put it in a bedroom cupboard on the first floor but not ideal, the preference would be in the loft. Is there a reason why the ground floor is the best place?

I'm think i'm going to ask my architect to contact the SE to spec the additional strengthening into the eaves required to house both an unvented cylinder - thinking 210l and the 400l accumulator are going to be pretty weighty - literally and figuratively!

Thanks again for your input, would you recommend a particular brand, or have any views on horizontal ones?

 

[Brambles]

The closer it ( the pumped accumulator) is to the mains incomer, the faster it will recharge. Ideally you want a vertical tank with the pump and control system mounted beneath the tank - to maximise the useable volume.

These are sizeable pumps and to minimise noise / vibration really need to be mounted on a solid floor.