Low Mains Pressure

[wysinawyg]

Help all!!

Been getting really quite worried and annoyed over the heating for our new place. SWMBO insists on a bath every morning and the en-suite (fed off an old and possibly knackered combi) at our new house isn't going to cut it without some fairly serious work. Piping to this has really been bodged with us only getting 9 l/min or so of flow and not a great deal of pressure (measurement awaited). Also, I think slightly unusually the mains feed goes through the bathroom before coming down to feed the combi. No possibility of an unvented system as it would be too much damamge to the house to retrofit because of the layout.

After much reading the options seems to be:

1. T off a mains feed from before the main stop cock and bring this directly into the extension (undesirable from a damage to the utility floor point of view and mess).

2. Some kind of tanking / pumping of water stored up in the utility at ground floor and then pumped through an unvented system / heat store.

Thoughts and reccomendations? We've a lot of room to work with and money not the most important factor. Is an all in one like the Grundfos home booster an option? or is it cheaper / better going for a big tank and getting the pump separately?

wysi

 

[Agile]

What does your plumber/heating engineer have to say about this?

 

[wysinawyg]

Very little. Unfortunately he's very much the plumber / jack of all trades rather than proper heating engineer. Original intention was just a bit of a facelift for the bathrooms and I don't think he has the experience.

He isn't corgi registered and would be getting a friend in to do a boiler swap (who I haven't yet ascertained if he has his ticket for unvented).

Its very much not the job I brought him in for so I was wanting to try and get an idea of the options before I probably end up going out to get someone else (with the options partly depending who I go and speak to).

wysi

 

[dom2466]

is the pressure and flow ok at you first tap ( normally the kitchen tap) fed directly from the service pipe ?
if No, then you may have a problem with your outside service pipe which can be renewed.
if YES, then it could be a number of reasons, your pump in your boiler may not be working or set at the low rate ( take a look on the side of the pump, normally a 3 stage switch which ajusts the pump rate)
your boiler as you say is OLD, may need renewed.

 

[gas4you]

If your combi is old then chances are it is only a 24Kw (80000btu) model. This would only be able to give around 9-10litres/min if brand new

 

[wysinawyg]

I think its pretty certain the old boiler needs to go.

Flow at the main kitchen tap is about 20 l/min and pressure is much better.

However the flow off the cold water tap in the utility (by the combi) is the bit thats only getting 9 l/min, the combi is giving off even less than that. Upstairs in the bathroom the flow doesn't drop off much at all to the cold taps.

Hence my thinking I need to do something with the water supply as well as the boiler. From what I understand I could put the biggest baddest combi/unvented boiler system in there but I'd never get a higher flow than the existing cold water tap up there, and its the 9 l/min it gives (as well as the 5 or 6 off the combi) which is wholly inadequate for my needs.

 

[Softus]

I think its pretty certain the old boiler needs to go.

It's pretty certain that you want it to go.

From what I understand I could put the biggest baddest combi/unvented boiler system in there but I'd never get a higher flow than the existing cold water tap up there

This shows that you understand, so it's even stranger that you want to replace the boiler.

 

[wysinawyg]

It's pretty certain that you want it to go.

Well, yes, kind of. As per the first post SWMBO demands a bath every morning. Even off the cold tap it takes 15 to 20 mins to run the bath and as we both work thats out of the question, sleep is too precious.

So we need a higher flow rate to use the bath. If we get a higher flow rate I don't think the 10 year old combi would heat the water quick enough even if serviced so it has (/I want it) to go.

This shows that you understand, so it's even stranger that you want to replace the boiler.

Well thats kind of the point, I've learnt enough to know that just replacing the boiler isn't going to give me what I want no matter how big and shiny a new boiler I go for. But also looking at combi specs the little thing we have at the moment isn't going to cut it no matter how close to optimum its working, nor I think is even one of the newer monstrous high speed combis.

Taking as the base point "I want to fill a 100(+ a bit?) litre bath in 5 minutes" whats the best way to go about it with a lowish pressure 10 l/min mains feed and no option of an unvented tank?

 

[simond]

If your standing pressure (measurement awaited) is sufficient the simple addition of an accumulator will allow you to fit either a fast flow combi, unvented or - if you fancy one, a heatstore.

We have, for instance, fitted 3 Power Store Vaillant 937s and a Worcester Highflow 440 off accumulators in the last 4 weeks in separate domestic dwellings.

Most households in the SE do not get more than 20l/m which these hybrid combis need to work satisfactorily when the washing machine fills etc.

 

[wysinawyg]

Thanks Simon. Do you have experience of pumping accumulators? It doesn't look to be something GAH offer but I have seen it offered by one manufacturer.

 

[gas4you]

However the flow off the cold water tap in the utility (by the combi) is the bit thats only getting 9 l/min

Have you thoroughly checked that there is not a 'ballofix' type of isolater partially shut in the cold supply to the utility?

 

[simond]

We do have experience of pumping accumulators but this is very rarely necessary and brings with it certain disadvantages.

GAH do have a pumping product shortly to be launched.

Please measure you standing pressure, Screwfix can sell you a gauge for about a tenner, or you could pick one up from your local plumbers merchant. With this measurement, it can be gleaned whether you need a pump or not.

In our neck of the woods, we have put in fast flow combis and unvented systems where other heating firms have said it is impossible. I quite like doing that