Low mains pressure & hot water systems (again)...

[DIYSOS]

I have a Victorian terraced property with a feeble water supply - 10L per minute (via 1/2 inch lead pipe), as measured at a kitchen sink and confirmed by the local water company. I will be putting in GCH soon - there is none at present (I'll probably put the radiator circuits in myself - Speedfit or similar under floorboards!). So there is to be a new a new boiler - t.b.d. but not a combi. I want to do 'something' about my feeble water system at the same time, probably getting rid of the old on-demand 'Main' gas water boiler which is in a bedroom wardrobe. But I won't be upgrading the mains water supply from the street.

There are two WC's and one bath/shower. The (thermostatic mixer) shower is just about adequate, but turning on multiple outlets (incl filling the bath) is hopeless!. The main thing is to get a decent flow when >1 outlet is turned on, though improving the pressure/flow to hot and some cold taps (eg bath) and particularly the existing shower would be a bonus. I don't want to spend too much (< ~500 ukp on top of CH & boiler would be good).

The obvious thing is to put a big cold water tank (or tanks) into the loft, which is large with good access. This to feed a new HW cylinder & non-potable cold water outlets, via a pump in some way.

Are there any other options I should consider?

I've read numerous posts in this area, as well as the faq, and there is indeed a lot of very good information - probably too much to completely take in!. As far as I could tell heatbanks, thermal stores and the like fall down on my low water pressure and/or my budget but tell me if I missed anything.

Thanks,

Paul.

[Doctor Evil]

Before going any futher. What pressure/flow do the water people say you would have if you upgraded your mains supply to a 25mm blue pipe? This determines which way you should design the system for now and in the future.

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[John]

Depending on just how high you can site your cold water storage tanks you may or may not need to worry about dynamic pressure to the shower. This might avoid the need for a shower booster pump but if you want to make provision "just in case" I'd suggest piping hot and cold to a suitable point where you could break into the pipework and install a suitable pump if you decide the available head simply isn't enough. Chances are you will never need it but at least the ground is prepared. Ensure you choose a suitably sized hot and cold tank outflow especially for long/convoluted runs also that the cold outlet is lower than the hot in case the storage tank runs empty (so anyone in the shower will not be momentarily scalded)

[DIYSOS]

Thanks for that advice - should come in useful.

I could also mention that I like the idea of running my (DIY Speedfit!) radiator circuits indirectly via some sort of thermal store or heatbank. This to prevent boiler over-cycling and hopefully limit any potential damage to the radiator circuits if there is a boiler fault. Are thermal store - type systems available where stored water from a big, slow-filling cold tank can be pumped through the 'thermal store' instead of the mains water supply to provide hot water?. Something like this might be an ideal solution, perhaps I'm describing something that is widely available under some name?

At this point I'm just about at, or beyond the limits of my understanding so I'm just hoping this makes some sense!.

Cheers - Paul aka DIYSOS

[Doctor Evil]

What you say can be done, but not as a package. A cold tank can have a pump off it that supplies the cold supplies and hot feed to a thermal store. An "integrated" thermal store with two cylinder stats to eliminate boiler cycling is what you want. Try Range Cylinders, web site below.

The cold tank can be anywhere, not just in the loft. For one man who was having a loft conversion done and all tanks removed, but with very poor water pressure (it was to be uprgraded in the district in 5 years time), I suggested putting the cold tank in the garage loft. This meant an underground blue pipe from the garage to the house at a point where the future new mains would enter. The booster pump (Grundfos Boost pump) was also in the garage. It fed a thermal store. So no water or pump noises in the hosue and high enough pressure of around 1 - 1.5 bar. I suggested putting some insulation around the tank in the rafters and have a small greenhouse heater run off a frost stat in case. He made a sort of insulated plywood room up there around the tank. The last I heard he still had it, not bothering to have the new mains run in when the district was updated. When the pumps plays up he probably will update the mains pipe.

Look at:

(make square stirage vessels) (make heat banks and storage vessels to size) (make thermal stores and stioarge vessels) (make cylindrical heat banks and storage vessels. Will make to order) (make heat banks and storage vessels) (make cylindrical thermal stores and storage vessels. (They are quite cheap and will make to order) make cylindrical thermal stores and storage vessels (make cylindrical thermal stores) _________________________________________ Usenet Zone Free Binaries Usenet Server More than 120,000 groups Unlimited download to open account

[Jeff]

Why not upgrade the main ? water co should make the connection FOC you only have to lay the pipe

Regards Jeff

[DIYSOS]

Too expensive and/or too much hassle for me and my considered opinion is I that won't be doing this..

Previous posters have reached the same conclusion in similar situations though in the end it's a fair option, and in some ways perhaps the best option, that some would want to take.

But I'll have enough to do for now putting in the CH circuits as it is...

Cheers, Paul.

[DIYSOS]

I asked ST a few months ago, from memory it was something like 1 bar - the same as current pressure as reported by a possible (at the time) CH installer after sticking a gauge onto the outside tap. Would the standing(?) pressure, unlike the flow rate, change much after upgrading the pipe?.

But upgrading the supply is off the table anyway unless there are severe problems with alternatives - hopefully not the case!.

Paul aka DIY SOS.

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Before going any futher. What pressure/flow do the water people say you would have if you upgraded your mains supply to a 25mm blue pipe? This determines which way you should design the system for now and in the future.

[Alex]

If you go the cold tank route erect a platform as high as possible for it to sit on,the higher the better,but at least a min of one meter above the shower head and balance this by bringing a seperate cold feed to the shower outlet direct from the tank.This will overcome most of your low pressure problems and will help to prevent drops in pressure when other outlets are open.

At my last house i had a head of 1.5 m and had a great shower without thermostatic valve and had no problems.

The platform needs to be built with bracing I would use 4x2 and bolt timbers together

Alex

[John Rumm]

alas not much, if at all...

[Christian McArdle]

Although I'm not sure you have the right reasons to install a heat bank, a standard unit will be as happy sitting on a traditional cold water tank with a shower pump as it would be on the mains. Indeed, it would work better than a traditional gravity cylinder, as there is no chance of sucking air down the vent pipe. You could also put the shower pump before the heat bank, which gives more "push" than "pull", which is good for the pump, and will reduce scaling, as cold water is less of a problem than hot.

Christian.

[Doctor Evil]

He wants a pumped system, so the tank can go anywhere, even at the end of the garden.

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[Christian McArdle]

However, some pressure is required in order to activate the flow switch, unless an accumulator/pressure based pumping system is used, which is likely to be more expensive than a simple flow switch shower pump. You can forget momentary switch activation on a system that supplies all the taps.

The pressure required to activate the switches may require some head, especially if a thermostatic mixer is used and check valves are used in preference to chocolate teapot hose clips that prevent you using the shower to wash out the bath/tray.

Christian.

[DIYSOS]

I'll use the term 'heatbank' (as it's DIY-able, I believe) in preference to thermal store...

So far, I think I'm starting to like this scheme. Then again I don't know how much these heatbanks cost yet, or how big it would need to be or where it would go!.

I'm thinking that, ideally, I'd have the boiler heat the primary mass of water in the heatbank -nothing else. Both the CH rads and HW would be secondary indirect throughputs, though I don't know if this is asking too much!. I could almost imagine getting a Corgi to put in the working boiler and heatbank, then add all the rest myself later (well, perhaps!).

I think I understand that using a good (say 1.5 or 3 bar) shower-type pump it would be possible to have a pumped HW, and CW supply to much of the house (excl drinking water taps of course) at reasonable pressure and cost - if the 9ft between the 1st floor heatbank (base) & loft floor CW tank gives enough head for the switches. And the bath might even take

[DIYSOS]

Well I'm finding technical info on various heatbanks but price info seems very hard to get on-line. If anyone knows of an on-line supplier with a good range & pricelist that would help alot.

Likewise collapsible tanks (I live in a Victorian terrace and the best place for the CW tank would be in the rear wing of the loft, accessable thru the

12inch rafters). I did get a quote for a 50 gallon collapsible tank from a local plumbers merchant, figure came in at ~120 ukp.

I'm still learning from your replies and many pervious posts. I've changed some of my ideas somewhat, but in principle still like the concept of a boiler heated thermal store & indirect/isolated HW and CH circuits.

For reference I had three quotes for CH recently. This was for slightly-larger-than-average Victorian 3 bed terrace, estimated heatloss of

16KW, with no existing CH. This in the Midlands, 2 zones + condensing boiler with the HW being left as-is. They all came it at about 6kukp. Had me reaching for the Speedfit without much ado. 2 wanted to put a GloWorm boiler in - not sure if that's because they're good for me or just convenient/profitable for them.

This thread is probably dead now but if anyone has any info on the above please post.

Thanks - Paul aka DIYSOS

[Christian McArdle]

The latest Glowworm is a different beast to those that preceded it. It has an outward firing cylindrical burner, which is a good alternative to a downward firing unit.

Christian.