Recommended Pressure/Flow Upgrade Path?

[DIY_Disasters]

Hi,

We have recently moved into a rural area into what I would call a "project". 4 bedroom house with 3 bathrooms. I have recently had the the gravity fed cylinder upgraded to an unvented cylinder for a few reasons

• Tank size increase from 140L to Gledhill 250L
• Plan on converting loft space so removal of header tanks
• Noise of shower booster previously in use was bad.

The G3 engineer that did the works did say that the system will not be as good as what I'm used to (came from new housing with oodles of pressure and flow). After the upgrade, I'd say the one shower we currently use is just about adequate but now I want to look at improving the system further to cope with future plans.

We have blue MDPE main supply coming into the house but I cant work out if its 25mm or 32mm, my gut says 25mm. The utility room tap nearest the main pumps out around 18lpm and we have around 1.6bar of static pressure and about 1.2bar of dynamic pressure when the utility sink tap is fully open. Unfortunately, the cold supply to the now new unvented cylinder is only 15mm from the main with around 16m of pipe work including the rise from ground to 1st floor.

The plan with the suites on the 1st floor is 2 showers and one bath. It would be nice to be able to have both showers providing a decent experience at the same time same time, but not essential. But I I would definitely like to improve the single shower experience we currently have.

So my question is this, is it worth upgrading the internal 15mm supply to the unvented to 22mm or should I just jump straight into a pumped accumulator like the Salamander AccuBoosts since the pressure of the system is not going to get me what I want anyway.

Thanks.

 

[oldbuffer]

1. Unless he / she was aware of the issues and your plans to overcome them, I think the plumber was unwise to install an unvented cylinder.
2. Your incoming pressure will be reduced by 0.4 to 0.5 bar at a shower head on the first floor, resulting in, say, (1.2 - 0.45) = 0.75 bar at the shower head.
3. I suspect your are going to need to boost the pressure anyway, so I would:
3a. Install the pumped accumulator.
3b. Then if necessary upgrade the cold feed to the unvented cylinder.

 

[DIY_Disasters]

He did mention a few times that the delivery is not going to be great and you could go with a shower booster pump that will power both showers when the upgrades do happen. But I couldn't cope with the noise of the existing booster pump. My eldest showers early in the morning so my youngest suffered the rath of the booster noise in his bedroom where the cylinder is housed. Equally the noise was bad in the living room below in the evening when the shower was in use so the plan was to go with unvented and upgrade pieces as we go along. We have no plans to move again so was happy to go this route.

The bath that is currently in place delivers around 12lpm when the cold is fully open so I guess this is indicative of the flow/pressure loss of the existing 15mm feeding the cylinder. I suspected that pressure was the main issue so a pumped accumulator would be the first step. As far as sizing, I presume bigger the better? What I'm trying to understand though is once the accumulator is empty would the pump still operate or would it switch off because it goes beyond the 12l/min allowance for direct mains boosting?

AccuBoost seem to be the big player in this space, but are there other manufactures/models I should consider?

Thanks.

 

[oldbutnotdead]

Yes it'll be worth replacing the 15mm supply to unvented with 22mm. When you do it, keep bends to a minimum, use swept bends not elbows, all that sort of stuff.
As for the rest, 16l/min at 1.6 bar is marginal for unvented dhw. You'd have had a much easier job keeping the vented (maybe with a 2nd 150l cylinder) and putting in boost pumps- when properly installed they are not intrusive.

 

[DIY_Disasters]

I did ask my plumber are they all noisy and he said yea, generally they are. Keeping the vented also ruled out the eventual attic conversion since the header tank was right in the middle of the loft. I guess it's too late now.

On the booster front, I have also seen the Stuart Turner ones. Are they much the same as the Salamanders? The pump on the Stuart Tuner uses 1300W compared to the 300W Salamander but I cant find figures for the pressure it delivers, only flow rate on the Salamander. The Stuart Turner one delivers around 4bar at 30lpm which I think would be ample for 2 showers delivering 15lpm each at the same time.

 

[oldbutnotdead]

Well at least you had a good reason to ditch the header tank. How's your surplus space at ground floor level- room for 500l unpressurized tank do you think? You can't pump-assist the water main by much into the building but you could just have a ball valve on said 500l tank and use a pump from the tank to maintain pressure/flow in your unvented cylinder. Re the pumps- it takes energy to send water uphill (which is what you are doing in a pressurised setup- 3 bar is equivalent to 30 metres vertical). 1300w has a much better chance of doing it than 300w, mebbe Salamander doesn't quote flow rate at dynamic pressure for a reason. Do remember that every hour the bigger pump runs will cost you 1.3kwh (units) of electricity- about 40p on my April tarrif

 

[DIY_Disasters]

I have a large enough utility to house a larder cupboard next to the boiler but I doubt that would take 500L, but if it can be housed outside or in the garage then I have plenty of room. My original thought was to house the accumulator and pump in a small shed at the side of the house which would be relatively near the main (3-4m), this would have the added benefit of putting the noisy pump outside. The garage on the other hand is miles away so probably not feasible. What's the difference between using a pressurised accumulator like the AccuBoost vs unpressurized container and a pump?

 

[oldbutnotdead]

Outside (sheltered from frost) is fine, just have pipe runs (22mm minimum) as straight as possible, maybe look at trace heating on the pipe. Accuboost etc is a turnkey solution (control gear etc built in and ready to go), tank and pump would prob be cheaper to buy but longer install time and more bits and pieces required (float switch in the tank so the pump doesn't run dry, bit more faff balancing hot and cold pressures).
If you're comfortable doing pipework yourself the tank/pump combo is diyable- Accuboost might require G3 again (and thus annual inspection)

 

[DIY_Disasters]

Really helpful info, thanks a lot. I guess with the 500L unpressurised tank you'd have more storage vs the accuboost before it runs out since the largest AccuBoost only holds half that I believe.

 

[DIY_Disasters]

Deleted

 

[oldbutnotdead]

Yup. Lots of modern water systems are designed to fit into the smallest space possible (due to how tiny modern houses are compared with 50s builds). If you have space you have many options to achieve your desired outcome and the modern stuff (with lots of engineering to reduce footprint) will almost certainly cost a lot more to buy than a less engineered bigger solution

 

[DIY_Disasters]

So something like this https://www.screwfix.com/p/polytank-cold-water-coffin-tank-100gallon-uk-1670-x-690-x-580mm/59841? What pump would you recommend for something like this?

 

[oldbutnotdead]

Pump wise you want something with the spec of that Stuart Turner job but continually rated (ie it will survive a 80% duty cycle- dedicated shower pumps will be designed around the timings for a typical single domestic shower, so maybe 20 mins in the hour at most. If your pump is boosting the whole house it'll be running for longer than that).
Don't suppose you own a nice big hill in your rural setting?- just a thought .

 

[DIY_Disasters]

Well the loft space is pretty big actually, so I could simply put the pumped breaker tank at one end and make a faux wall when it comes to the conversion. At least that would be higher in the loft than the ground floor and the conversion to 22mm to the cylinder would be easy, but then we go back to the whole point of changing to an unvented in the first place

 

[oldbutnotdead]

Absolutely- you want the space for people & you want the noise in an outhouse. If you need a pump of any sort then put the tankage in the outhouse.