combi shower

[mark.s]

Hi all
I am trying to solve the problem of the water flow/pressure dropping in my combination boiler/shower set-up when other taps/appliances are turned on. I'm not a plumber, but just had a thought, has any one ever fitted an on demand pump to the inlet side of the boiler that pushes the water through it at a constant rate/presure?

any thoughts on this would be much appreciated

 

[mikegas]

Is your cold ok? You can only get what your combi is capable of giving out, if your combi is giving its max lpm then adding a pump via a tank won't help

 

[mark.s]

I should point out mikegas, all taps/appliances are mains supplied, i.e no cold water tank, so when another cold tap/appliance is turned on somewhere in the house it seems to 'starve' the boiler of it's cold water supply so i thought maybe a pump connected the the cold water inlet on the boiler would keep the supply constant. The flow is fine until something else is turned on.

Just a thought, maybe i've got it wrong and should have a cold water tank top supply cold taps/appliances?

 

[mikegas]

I mentioned a tank because you can't pump direct from the main

 

[mark.s]

I can't see why you can't pump from the mains, i'm not talking about a power shower pump, more of a pump that just supplies the maximum amount my boiler is capable of suppling.

When you say you can't pump direct from the main, do you mean it just won't physicaly work or are there some regulations that say you can't?

 

[Puddle]

This is usually a problem with outlets in the kitchen,ie when you are in the shower someone fills a kettle or turns washing machine on,maybe try fitting a restrictor valve on these out lets,if you have a good mains supply,this will improve the situation

imho

 

[kay-jay]

yes regs prevent a pump fitted on mains supply unless it is only capable of pumping less than 12l/min.

basically all that comes out of a combi is what goes in, so check your incoming mains pressure, also what kw is the boiler? lower kw= lower flow on hot water side of supply. do as puddle suggests and add restrictors to kitchen taps etc, to help but may be something you need to just put up with.

 

[mark.s]

Thanks Puddle

Would it be a good idea for me to fit a water tank to supply kitchen cold tap/appliances/toilet etc and just leave the boiler on the mains, if that worked could i fit some thing to stop the tank filling while the boiler is still supplying hot water? (sorry don't really know what i'm talking about, just thinking out loud!)

Cheers

 

[Mike Jackson]

I can't see why you can't pump from the mains, i'm not talking about a power shower pump, more of a pump that just supplies the maximum amount my boiler is capable of suppling.

When you say you can't pump direct from the main, do you mean it just won't physicaly work or are there some regulations that say you can't?

It's the water regulations that state that you can't pump direct from the main. You can cause all sorts of problems from starving other properties of water to creating backflow from other properties and contaminating the cold main.

 

[Howsie]

Kitchen cold tap must be supplied directly from the mains.

 

[Howsie]

Mark.s what size property do you have?

 

[mark.s]

Kay-jay, i understand that "all that comes out of a combi is what goes in", my problem is there isn't enough going in so there isn't enough coming out.
Thanks for the advice about the pump but "something you need to just put up with" is a typical tradesmans answer to something he doesn't have a solution to!

 

[kay-jay]

Kay-jay, i understand that "all that comes out of a combi is what goes in", my problem is there isn't enough going in so there isn't enough coming out.
Thanks for the advice about the pump but "something you need to just put up with" is a typical tradesmans answer to something he doesn't have a solution to!

the solution is upgrade mains supply and buy a bigger boiler! unless particularly affluent you will end up 'living with it' there is no quick fix for this but as said restrictors will lessen the effect but not cure it!

 

[mark.s]

Thanks Howsie, Good point

 

[kay-jay]

p.s there are pro's and cons to each type of system non are perfect and some kind of compromise is required. you are learning what the limitations of a combi boiler are when feeding a shower.

 

[dancinplumba]

you can put a pump on main but it must be a s kay-jay has said 12l/m max and you will need permission from water supplier, which is unlikely that you will get it, do as puddle says and put restricteos on outlets and try putting an accumulator on feed to combi with a check valve.
imo

 

[kay-jay]

would it really be too difficult to say ' im jumping in the shower, don't run any taps for 5 mins?

mountains and molehills imo

 

[glenno1]

If you put a pump on incoming main you will cause yourself endless amount of problems forcing water through the combi would not be recommended

 

[mark.s]

I'm getting 2 answers now, one says i can pump the mains at 12l/minute and one which says i can't pump the main which one is right!

I don't think the boiler size isn't the problem it's 37kw, it's trying to get a constant/cosistant flow through it when other taps/appliances are turned on.

 

[mark.s]

' im jumping in the shower, don't run any taps for 5 mins?'

is that your solution!

 

[dancinplumba]

you need permission from water supply company to put any size pump on mains, they will probs not give you permission, because it robs other users of water, put accumulator on cold supply to combi
imo

 

[dancinplumba]

pay your water company to increase supply pipe to your property

 

[ManchesterGas]

Is the main cold feed to the property in lead or alcathene?

What is the flow rate of the kitchen tap with and without the outside tap on full?

 

[kay-jay]

' im jumping in the shower, don't run any taps for 5 mins?'

is that your solution!

its not a great hardship though is it. if you want to throw money at it go ahead

 

[mark.s]

"If you put a pump on incoming main you will cause yourself endless amount of problems forcing water through the combi would not be recommended"

What are these endless problems i would cause if i only pump it through at the recommended rate? surely mains pressure forces it's way through the boiler?