Low flow what do i need to increase

[Ahmiccc]

Hi All,

 

I'm having issues with low hot water flow when cold tap is open, the house is a full reno and so everything has been stripped back and all we have regards plumbing in the house now is a sink with cold water only right now and then a bath with cold and hot water, we have also two radiators connected up just to help with a little heating when working in the house over winter.

 

I've recently installed a new 32 mm MDPE water mains (upgraded from 15mm) into my house from this drops down to 28mm then 22mm stop tap and then onto a mixture of 15mm plastic and copper up to boiler and also all taps (this is all temporary) I still have the 15mm mains connected for now main water mains but isolated on internal stop tap. Severn Trent say the pressure in the area is 2.1 bar so this is maximum I can get and do get is 2.1 bar static pressure, when one tap is open i get varying between 0.8-1.2 bar dynamic pressure.

 

I have a Worcester Bosch 28cdi compact combi boiler rated to 10.6l a minute hot water new boiler bought start of this year maybe this is my first mistake and under rated what I needed. but I'm looking to see if I can rectify this mistake maybe and hopefully without having to replace my boiler. From this boiler I will of course be getting hot water but also this boiler closed loop system will be feeding into a buffer tank and then the buffer tank will essentially feed UFH for both floors, storage tank is there to stop short cycling.

 

The only space i have is to have all this in the attic, so my boiler is in the attic and the UFH buffer tank is in the attic if I need to add an accumulator or unvented tank or hot water storage tank or nay other option this would also have to be fitted in the attic. Its a 90m2 house that's two floors combined and then an attic on top which is just storage and now probably my plumbing hub. In the house there will be a possibility of having 2 showers and 3 taps running at one time, that's garden tap whether that's watering or washing the car or whatever, the kitchen tap and then utility sink tap, this is worst case scenario but what I know I definitely want to cover my self for is definitely having two showers running at the same time and taps is something we can easily work around.

 

The whole house will be water softened which will be installed also, the only water that wont be softened is kitchen and utility cold water taps.

 

So these are the results I'm getting from the l/min jug, from my taps and I'm only going to be putting up the findings from the 32mm MDPE pipe opened up. the jug measures a maximum of 24l/min, so when I have one tap open the water is overflowing from the jug, so more than 24l/min but its only just trickling over the jug so maybe around 30l/min, when I open up two taps, sink downstairs next to stop top and up stairs bathroom tap right above stop tap I get around 16l/min on upstairs tap, didn't measure what I get downstairs as well to add them up. on non of the taps are there restrictors either so full bore what the pipe allows is what comes out.

 

When I close all taps and just open up hot water top i get 10l/min which seems right as that's what boiler is rated to, the problem is I keep my hot water tap open and then when I open one tap the hot water drops down to not even 3l/min and the cold water is around 24l/min so obviously my hot water I don't have enough flow.

 

My dilemma is what do I install to have essentially a good enough hot water flow to both my showers don't know whether its accumulator for cold water, whether its an unvented indirect cylinder or hot water storage tank indirect, or if there is anything else that would be better?

 

 

Below are the tanks I've been looking at but don't know what's best for my situation or do i need to look for different spec tanks or as above what else would you recommend, bearing in mind I don't want to replace my boiler.

 

Indirect unvented cylinder

https://www.heatandplumb.com/acatalog/heatrae-sadia-megaflo-eco-systemready-hot-water-cylinder-95050499?utm_source=google&utm_medium=Shopping&gclid=CjwKCAiAtdGNBhAmEiwAWxGcUq-jadTirtJZKQErEoWJ8zMcKBQ0KsvsirPMZYLAMwUi7kxncDgVNxoCt00QAvD_BwE

 

Accumulator tank

https://pumpexpress.co.uk/shop/pressurewave-series-150-litre-vertical-pressure-vessel/

[JohnMo]

Long post.

 

So cold water that feeds the boiler in the loft is taking the easiest route to come out of the cold taps, instead of the more restrictive route into the loft where you have the boiler.

 

Your boiler will not support a UVC as it's a combi.  The flow rate may not support more than one shower at a time, unless they have restricted flow.

 

Have a read of the attached to get an idea of what you can do to improve what you have.

 

A plumber will need to jump in on how to balance your flows.

Canetis-SuperFlow-Product-Sheet-WE-050318.pdf Combi-SuperFlow-White-Paper-v1-2-4.pdf

[Ahmiccc]

20 hours ago, JohnMo said:

Long post.

 

So cold water that feeds the boiler in the loft is taking the easiest route to come out of the cold taps, instead of the more restrictive route into the loft where you have the boiler.

 

Your boiler will not support a UVC as it's a combi.  The flow rate may not support more than one shower at a time, unless they have restricted flow.

 

Have a read of the attached to get an idea of what you can do to improve what you have.

 

A plumber will need to jump in on how to balance your flows.

Canetis-SuperFlow-Product-Sheet-WE-050318.pdf 322.43 kB · 6 downloads Combi-SuperFlow-White-Paper-v1-2-4.pdf 960.61 kB · 4 downloads

Hi John,

 

cheers for this but still doesn't seem to improve my problem of more flow to be able to provide for 2 showers and taps.

 

the UVC wont be ultra violet it'll be a salt type softener.

 

looking for a solution to increase flow essentially and to be able to supply two showers 

 

Ive been looking into maybe using an unvented cylinder but as a hot water storage so instead of cold water feed at the bottom i have that going into a pump then that feeds the showers which is where i will get the flow and then feeding into the tank i have hot water from the boiler feeding into the tank, i hope that makes sense.

[Mr Punter]

Not read all but a cold water accumulator with pump is often recommended for pressure/ flow issues.

[Ahmiccc]

7 hours ago, Mr Punter said:

Not read all but a cold water accumulator with pump is often recommended for pressure/ flow issues.

Thanks mr punter

 

from my understanding an accumulator will help with keeping my boiler putting at the most amount of hot water possible which is 10.6l/min but I require more if I were to run two showers I think

[Mr Punter]

It is true that you won't get enough flow for 2 showers with the combi you have but the accumulator will help with pressure and flow rates and hot / cold imbalance.  If you really want to run 2 showers at once you additionally need either a hot water cylinder or a high flow storage combi,

[SteamyTea]

 

[Ahmiccc]

9 hours ago, Mr Punter said:

It is true that you won't get enough flow for 2 showers with the combi you have but the accumulator will help with pressure and flow rates and hot / cold imbalance.  If you really want to run 2 showers at once you additionally need either a hot water cylinder or a high flow storage combi,

I’ll be posting here Shorty of a theory I’ve been thinking hopefully to try, using a UVC as a hot water storage and then pump pumping around 20l/min then restrictors on showers for 10l/min each on hot water side.

[Ahmiccc]

6 hours ago, SteamyTea said:

 

Can’t find anything in here to resolve my issue of providing good hot water flow to two showers sadly

[Nickfromwales]

On 13/12/2021 at 12:30, Ahmiccc said:

Hi John,

 

cheers for this but still doesn't seem to improve my problem of more flow to be able to provide for 2 showers and taps.

 

the UVC wont be ultra violet it'll be a salt type softener.

 

looking for a solution to increase flow essentially and to be able to supply two showers 

 

Ive been looking into maybe using an unvented cylinder but as a hot water storage so instead of cold water feed at the bottom i have that going into a pump then that feeds the showers which is where i will get the flow and then feeding into the tank i have hot water from the boiler feeding into the tank, i hope that makes sense.

Hi.

OK, you seem to be all over the place with the replies here, so let me clear a path for you.

On 12/12/2021 at 15:33, JohnMo said:

Your boiler will not support a UVC as it's a combi.

Incorrect. The heating circuit can easily support an UVC / TS etc, simply by adding 2-port zone valves to split the heating flow and then running that to the heating coil of the storage tank. The downside is that the combi then, ideally, wouldn't be used as the return path for the hot water a) due to the restrictions through the combi plate heat exchanger, and b) because the combi does one job or the other, eg DHW or heating out, not both together. This means that all the time DHW flows through the combi, it will ignore the heating circuit completely thus not maintaining the temp of the UVC.

 

To get 2 showers running simultaneously, and with good flow, you will definitely need to store hot water in an UVC. I would not recommend the pump as with the new cold mains in place you should find things 'sufficient' as is. You'll lose the inherent restrictions, in-built into the DHW gubbings of a combi, by going mains > UVC > outlets, plus the hot and cold feeds to all the mixer outlets will also be balanced by the control group supplied with the UVC. That gives a 22mm outlet to the UVC and a 22mm outlet to cold mixer feeds, both at the same potential. For this setup you will need to plumb the house correctly, with all monoblock taps / mixers etc all piped back to the same place at the UVC. Cold feed appliances, WC's, and DEFFO the outside tap need to be tee'd off the cold mains the second it comes into the house. Ideally the outside tap should come off the rising cold mains before the first domestic stopcock within the property.

The combi can be run to the most infrequently used hot tap in the house, and the one open for as little a time period as possible ( probably the cloakroom wash basin ) so the DHW priority when it's in DHW mode is not dominated by that outlet eg it stops servicing heating output to rads / UVC.

Ignore the dynamic pressure readings as they are academic, because you can get great performance from a shower with little to zero dynamic pressure. It's flow rate l/p/m that matters here.

Plumb the house to have a rising dedicated 22mm cold feed that services the UVC only to maximise performance.    

[Ahmiccc]

Hi Nick, not to do any one down but I've seen you around on these forums and was hoping you would respond to this question, you've cleared a path for me i just need it rectifying a little fuzzy in some areas, don't mean to sound cliché. I've put my comments and questions in red.

 

9 hours ago, Nickfromwales said:

Hi.

OK, you seem to be all over the place with the replies here, so let me clear a path for you.

Incorrect. The heating circuit can easily support an UVC / TS etc, simply by adding 2-port zone valves to split the heating flow and then running that to the heating coil of the storage tank. The downside is that the combi then, ideally, wouldn't be used as the return path for the hot water a) due to the restrictions through the combi plate heat exchanger, and b) because the combi does one job or the other, eg DHW or heating out, not both together. This means that all the time DHW flows through the combi, it will ignore the heating circuit completely thus not maintaining the temp of the UVC.

So I  believe this will tie in to your point below regards hot water not being tied into the return path, so essentially my boiler wont be plumbed in for hot water just for heating ? as the hot water will come directly from the UVC ?

9 hours ago, Nickfromwales said:

 

To get 2 showers running simultaneously, and with good flow, you will definitely need to store hot water in an UVC. I would not recommend the pump as with the new cold mains in place you should find things 'sufficient' as is. You'll lose the inherent restrictions, in-built into the DHW gubbings of a combi, by going mains > UVC > outlets, plus the hot and cold feeds to all the mixer outlets will also be balanced by the control group supplied with the UVC. That gives a 22mm outlet to the UVC and a 22mm outlet to cold mixer feeds, both at the same potential.

So the point of mains > UVC > outlets, it wont be going through my boiler at all so as to repeat essentially from above ? will the heating of the water regards the coil and boiler be sufficient enough to provide me with hot water ? and regards this, does this then mean I should be getting same flow as cold water for my hot water ? or there about ? which i believe will be enough to run two showers at once.

 

9 hours ago, Nickfromwales said:

For this setup you will need to plumb the house correctly, with all monoblock taps / mixers etc all piped back to the same place at the UVC. Cold feed appliances, WC's, and DEFFO the outside tap need to be tee'd off the cold mains the second it comes into the house. Ideally the outside tap should come off the rising cold mains before the first domestic stopcock within the property.

Yes the plumbing wont be a problem that I've got my head around, in this instance im wanting a salt water softener, would it be good to have the water softener plumbed in before the UVC as I live in a hard water area and it'd increase the life span of all my appliances/boiler and also i hate the sight of water drops where they leave a residue if not wiped off straight after a shower, this will be only plumbed into my appliances and not the sinks in utility and kitchen due to water taste. So how i see this going out is as follows:

Mains |-> water softener -> UVC -> outlets (or does it need to go UVC boiler then outlets as with boiler im then limtied ot 10.6l/min)

 (tee)  |-> Kitchen and utility cold water.

 

The kitchen and cold water wont be used so much when showering.

9 hours ago, Nickfromwales said:

The combi can be run to the most infrequently used hot tap in the house, and the one open for as little a time period as possible ( probably the cloakroom wash basin ) so the DHW priority when it's in DHW mode is not dominated by that outlet eg it stops servicing heating output to rads / UVC.

Ignore the dynamic pressure readings as they are academic, because you can get great performance from a shower with little to zero dynamic pressure. It's flow rate l/p/m that matters here.

Plumb the house to have a rising dedicated 22mm cold feed that services the UVC only to maximise performance.    

Sounds great that will plan out that utility tap wont use much hot water mainly showers then kitchen sink.

I think ill have the room but i think it can only be better if i plumbed it to a rising 28mm i know the UVC reduces it down to 22m just future proofing really ?

 

Once again thanks for the response and going through these points. 

[Nickfromwales]

50 minutes ago, Ahmiccc said:

So I  believe this will tie in to your point below regards hot water not being tied into the return path, so essentially my boiler wont be plumbed in for hot water just for heating ? as the hot water will come directly from the UVC ?

The combi will have a cold mains feed, teed off in 15mm before the control group. The hot outlet of that will be 15mm pipe to the low use outlet and that alone. One pipe one outlet. 
DHW will come from the UVC for everything else. 
 

50 minutes ago, Ahmiccc said:

So the point of mains > UVC > outlets, it wont be going through my boiler at all so as to repeat essentially from above ? will the heating of the water regards the coil and boiler be sufficient enough to provide me with hot water ? and regards this, does this then mean I should be getting same flow as cold water for my hot water ? or there about ? which i believe will be enough to run two showers at once.

As above re flow of mains through combi. 
As long as the rising main gives the UVC what is called “cold mains priority”, eg the 22mm feed from stopcock to control group uninterrupted, then you’ll be as well off as you’re going to get. 
To maximise the preservation of the flow rates the outside tap should come from the rising cold mains BEFORE the first ( aforementioned ) stopcock.
The cold fed domestic appliances and the WC’s should all then be fed from the softener cold outlet, with the softener being the very first thing off the stopcock. Stockcock > double check non return valve > drain off cock > 22mm tee. Off that tee comes the 22mm feed to the softener, and the 22mm cold feed to the UVC control group. Some may call this a bit OTT, but with a promise of no more than 2.1 bar and expected struggles with max flow rates, do this and max out your situation is my advice and what I would 100% do if this was one of my client’s full M&E projects. Soften everything other than the kitchen sink cold, American fridge cold feed, possibly the utility cold, or any other cold outlet routinely used for human consumption. Combi-mate conditioners can be used for treating the raw ( hard ) cold feed before these outlets / appliances ( like a boiling / chilled water faucet ) for max results. As always, follow the specific MI’s ( manufacturers instructions / installation advice ) for the items you wish to purchase, so knowing right now what is going in is paramount for this design to be right first time. MI’s can be downloaded for most common devices. 

Running 2 showers simultaneously will need a household discipline of no other significant outlets being used in parallel during shower times. Both combi boilers and UVC’s are cold mains dependant so ultimately use that cold mains potential and nothing else to push the hot water to the outlets. Starving them obviously had a detrimental effect, however with the static body of pre-heated DHW in the UVC, you will benefit from ‘same temp’ showers which just speed up or slow down, whereas with a combi they would just go cool / cold. Good quality thermostatic shower mixers for balanced pressure cold / hot systems is vital. Do not cheap out there. 
28mm is OTT imho, as the above splits the 22mm main at the stopcock already.

I would say allow space to add a 200 or 300L cold mains accumulator if there is room in a garage / ground floor space, and have that in the pipe run between the 22mm priority run and the control group so it’s only ever fortifying bathing / showering / mixer taps. Consider that as a parachute option for the eventuality of when the new mains becomes live and you have the system finished, you’re not happy with the max flow rates for the 2 showers together. 

[SteamyTea]

Just how important is flow and temperature stability for your showers.

The easy, and cheap way to get both is a vented DHW cylinder with a cold takeoff from the F&E. Then pumps for the showers. Only think to be wary off is overpumping and damaging the cylinder. But that can be calculated at no cost.

Edited December 15, 2021 by SteamyTea

[Nickfromwales]

7 hours ago, SteamyTea said:

Just how important is flow and temperature stability for your showers.

It’s very important to most, hence it’s frequently discussed here. 
Why would you put pumps in and large CWS storage tank(s) when you could have a quieter, more efficient system?

Plus the hot tank needs a certain amount of head for gravity then for all the other outlets that cannot be fed from the pump. 
No thanks ?

CWS for a pumped gravity arrangement in this particular instance would need to be 75gal minimum. 

[SteamyTea]

38 minutes ago, Nickfromwales said:

very important to most, hence it’s frequently discussed here.

Hence I offer an alternative that also works.

 

38 minutes ago, Nickfromwales said:

CWS for a pumped gravity arrangement in this particular instance would need to be 75gal minimum. 

You doing get something for nothing.

 

[Nickfromwales]

2 hours ago, SteamyTea said:

Hence I offer an alternative that also works.

A model T Ford will get me from Lands end to John-o-scrote, eventually, but I would rather drive it in its modern day equivalent ( particularly if the modern choice was about the same price with cheaper running costs, less things to go wrong, and a lifetime warranty when bought in stainless ).

Edited December 15, 2021 by Nickfromwales

[Ahmiccc]

12 hours ago, Nickfromwales said:

The combi will have a cold mains feed, teed off in 15mm before the control group. The hot outlet of that will be 15mm pipe to the low use outlet and that alone. One pipe one outlet. 
DHW will come from the UVC for everything else. 

That sounds awesome brilliant thankyou!

 

Quote

As above re flow of mains through combi. 
As long as the rising main gives the UVC what is called “cold mains priority”, eg the 22mm feed from stopcock to control group uninterrupted, then you’ll be as well off as you’re going to get.

Wont be nothing from cold mains can do that no problem, but to get cold water to boiler would i then go from the control group ? or have to interrupt the mains and have a 15mm tee of for boiler ?

 

Quote

To maximise the preservation of the flow rates the outside tap should come from the rising cold mains BEFORE the first ( aforementioned ) stopcock.
The cold fed domestic appliances and the WC’s should all then be fed from the softener cold outlet, with the softener being the very first thing off the stopcock. Stockcock > double check non return valve > drain off cock > 22mm tee. Off that tee comes the 22mm feed to the softener, and the 22mm cold feed to the UVC control group. Some may call this a bit OTT, but with a promise of no more than 2.1 bar and expected struggles with max flow rates, do this and max out your situation is my advice and what I would 100% do if this was one of my client’s full M&E projects. Soften everything other than the kitchen sink cold, American fridge cold feed, possibly the utility cold, or any other cold outlet routinely used for human consumption. Combi-mate conditioners can be used for treating the raw ( hard ) cold feed before these outlets / appliances ( like a boiling / chilled water faucet ) for max results. As always, follow the specific MI’s ( manufacturers instructions / installation advice ) for the items you wish to purchase, so knowing right now what is going in is paramount for this design to be right first time. MI’s can be downloaded for most common devices. 

Ideally id like soft water on the hot water to showers just to stop the water droplets really so ill go with the combi mate conditioner for them I think that would be best idea. rather than trying to figure out how to through the water softener in there then back up and so forth.

 

Quote

Running 2 showers simultaneously will need a household discipline of no other significant outlets being used in parallel during shower times. Both combi boilers and UVC’s are cold mains dependant so ultimately use that cold mains potential and nothing else to push the hot water to the outlets. Starving them obviously had a detrimental effect, however with the static body of pre-heated DHW in the UVC, you will benefit from ‘same temp’ showers which just speed up or slow down, whereas with a combi they would just go cool / cold. Good quality thermostatic shower mixers for balanced pressure cold / hot systems is vital. Do not cheap out there. 

Yeah when two showers running there wont be anything else running and even the two showers running it wont be for long, regards the UVC i was thinking around a 210L tank to be enough for my needs would you agree ? thinking like something linked below: as id like the ability ot possibly even have a heater in place just as a back up really just the possibility more than a requirement i think the below allows that.

http://www.advancedwater.co.uk/prod-218-088-2120.html

 

Quote

28mm is OTT imho, as the above splits the 22mm main at the stopcock already.

I would say allow space to add a 200 or 300L cold mains accumulator if there is room in a garage / ground floor space, and have that in the pipe run between the 22mm priority run and the control group so it’s only ever fortifying bathing / showering / mixer taps. Consider that as a parachute option for the eventuality of when the new mains becomes live and you have the system finished, you’re not happy with the max flow rates for the 2 showers together. 

When you say 300l accumulator I'm guessing you mean a 300l mains accumulator but in regards to how much fits in tank is around 180L of water as the rest is the bladder ? just wanted to clear this. something like the below.

https://www.anglianpumping.com/product/accumulator-tanks/300-litre-accumulator-vertical-gws?gclid=Cj0KCQiAweaNBhDEARIsAJ5hwben8ggq5t9p1ioKusX_9_hCjd6j77v8MVHhgRabYAJrMokmlzDPhVcaArfDEALw_wcB

Edited December 15, 2021 by Ahmiccc

[Nickfromwales]

12 hours ago, Ahmiccc said:

That sounds awesome brilliant thankyou!

On reflection, the hot water pipe from the combo to the low use outlet can be in 10mm pipe. That will have lower dead leg characteristics and deliver hot water quite a lot quicker to that outlet. I do this a lot, works very well with plenty of flow rate.

12 hours ago, Ahmiccc said:

Wont be nothing from cold mains can do that no problem, but to get cold water to boiler would i then go from the control group ? or have to interrupt the mains and have a 15mm tee of for boiler ?

Answered in my previous, tee off before the control group.

12 hours ago, Ahmiccc said:

Ideally id like soft water on the hot water to showers just to stop the water droplets really so ill go with the combi mate conditioner for them I think that would be best idea. rather than trying to figure out how to through the water softener in there then back up and so forth.

No. You’ll have cold and hot water blended, so if they’re not both from a softener then you’ll still have issues with limescale / furring up of outlets. Softener at the stopcock and everything from that. Softener needs to be before the control group so there is no practical way of sensibly integrating it between / across the balanced and unbalanced ( pre and post control group ) supplies afaic. Adds unnecessary complication and will not protect your appliances / outlets as it is intended to do. Why buy and install a softener to do half a job? 
So no   
 

 

12 hours ago, Ahmiccc said:

Yeah when two showers running there wont be anything else running and even the two showers running it wont be for long, regards the UVC i was thinking around a 210L tank to be enough for my needs would you agree ? thinking like something linked below: as id like the ability ot possibly even have a heater in place just as a back up really…

Get in touch with Trevor@cylinders2go and mention my username and the forum and he will give you a discount on the UVC. It would be a Telford stainless unit, and you can have one or more immersion heaters, with a lifetime warranty. Plenty of members on here have purchased via him.

12 hours ago, Ahmiccc said:

When you say 300l accumulator I'm guessing you mean a 300l mains accumulator but in regards to how much fits in tank is around 180L of water as the rest is the bladder ?

With your stats, you’ll probably get 130-150L useful average storage from a 300L acc.

I buy Zimlet units from Anchor Pumps. 

[Ahmiccc]

9 hours ago, Nickfromwales said:

On reflection, the hot water pipe from the combo to the low use outlet can be in 10mm pipe. That will have lower dead leg characteristics and deliver hot water quite a lot quicker to that outlet. I do this a lot, works very well with plenty of flow rate.

Answered in my previous, tee off before the control group.

No. You’ll have cold and hot water blended, so if they’re not both from a softener then you’ll still have issues with limescale / furring up of outlets. Softener at the stopcock and everything from that. Softener needs to be before the control group so there is no practical way of sensibly integrating it between / across the balanced and unbalanced ( pre and post control group ) supplies afaic. Adds unnecessary complication and will not protect your appliances / outlets as it is intended to do. Why buy and install a softener to do half a job? 
So no   
 

 

Get in touch with Trevor@cylinders2go and mention my username and the forum and he will give you a discount on the UVC. It would be a Telford stainless unit, and you can have one or more immersion heaters, with a lifetime warranty. Plenty of members on here have purchased via him.

With your stats, you’ll probably get 130-150L useful average storage from a 300L acc.

I buy Zimlet units from Anchor Pumps. 

That’s smashing I’ve got my head round it all now regards the hot water side and uvc and everything so Thankyou for that and will definitely take your advice on the UVC from Trevor and also the accumulator, just a one last queerly I think, and I’ll leave the water softener out of the equation so won’t be installing that but for the cold water taps and appliances and so on, where would I take the water from would I take the water mains up to attic then tee off there and bring back down to taps and appliances or, can I Tee off from ground floor before going up to supply them all or would it go from UVC blender group valve which connects the HW out from uvc and CW in to blend ?

if so how does this blender know what temperature I want at taps ? Or am I barking up the wrong tree