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ajl · Joined: 11 Aug 2003 Posts: 3 Location: herts

Experts,
Apologies in advance for the length of prose. I have moved into an older house in which the gravity (large bore) central heating has been replaced by modern plumbing, but the hot water supply still runs in iron 2inch+ pipe. The boiler and copper cylinder are located in a cellar at one end of the house. Vertically above on the first floor are two en-suite bathrooms, about 20ft horizontally also on the first floor is a third bathroom in the middle of the house, and the kitchen on the ground floor is located about 35ft from the boiler. There is also a ground floor utility room located above the cellar where the boiler is located. Currently all are supplied from a 3 and 2 inch steel circulation loop running from the cylinder up to under the first floor and along to the third bathroom. There is also an old towel rail heated by this loop. The kitchen is supplied from a 1 1/2 leg off the loop. The cold water tank is located in the loft vertically above the kitchen and supplies the hot water circuit via a 3inch line directly (more than 40 ft).

The system works ok except that
-the hot water in the cylinder cools off quickly with the heat loss from the circulation loop and the towel rail
- the towel rail on the circulation loop continually gasses up and eventually water in the kitchen splutters
- 'senior management' is complaining about 'black bits' in the hot water in the bath
- 'other management' complains about the lack of shower pressure elsewhere
- the middle bathroom needs upgrading to state of the art.

I assume that the 'black bits' are oxidisation of the hot water circulation loop steel.

I was considering replacing the circulation loop with a single supply, removing the towel rail from the hot water circuit, and also moving the cold water tank to the roof space vertically above the boiler. However I still feel that there may be a pressure problem on the showers, and wondered whether moving to a totally pumped system for cold and hot in the house would be a solution.

Your advice or experience welcomed.

thescruff · Moderator Joined: 03 May 2003 Posts: 4619 Location: Bath

The secondary return on a large system is essential to save water, the heat loss from the circuit which should be lagged, would be no different than running the tap for 5mins waiting for it to draw hot water.

Black bits, air/gas in rads all equates to a system that's passed its sell by date, and will soon need attention.

To answer your pump question, Don't even think about connecting a pump to your water system, it will disintegrate.

Presuming one has a golden goose in the basement, I would consider fitting a large sectional storage tank in the basement alongside the boiler and cylinder with a pumpset to supply the house, ( and I don't mean shower pumps).

It would however mean replacing, all the old galvanised pipe, a major job and not cheap.

regards

scruff

Dan Robinson · Posted: Fri Sep 12, 2003 8:49 pm Post subject:

Agree with scruff that the system sounds like it needs a complete overhaul.

However before going for the pumped breaker system scruff is suggestiung (which has some good advantages), what is your water pressure like? Do you know what water main feeding your house like?

If is any good, you may consider an unvented tank. Mains presure and floow rates to all outlets.

ajl · Joined: 11 Aug 2003 Posts: 3 Location: herts

Experts,
Thanks for the analysis and advice and also maybe confirmation that the old pipework needs an overhaul. Yes, knew it would be expensive....

Following up the break tank in the cellar idea, a piece of smart lateral thinking which I had not considered, the cellar headroom is just over 2 metres. Do I need to consider any head restrictions and what size of tank capacity should I be considering? Assume
- the pump would be lined up to supply the cylinder and not after it, and
- the 'sectional tank' is needed for ease of access assuming the entrance to the cellar is tight?

The alternative of mains-driven system is interesting. Main in road has just been renewed with plastic. House is on top of hill. Are there any parameters I could use to check suitability (such as pressure and flowrate from exisiting taps connected to mains)?

Many thanks so far.

Dan Robinson · Posted: Sat Sep 13, 2003 8:26 am Post subject:

The break tank idea is one that we have successfully use a few times; and has the advantage of constant pressure and and backup should the street supply fail.

however, there is the expense of the pumps (Two Stuart Turner 3 Bar Negative Head Singles) which one day would go wrong.

For the unvented; it is only really worth doing if you have 2.5 bar and 20 or more litres per minute flow rate. If the flow rate is low but you have the pressure, then chances are you have an old lead water main and should upgrade it to 32mm MDPE. If you are removing all the old pipework (well at least the lead) then you may be able to come to some arrangement with the water board over cost.

Also if you are thinking of an unvented cylinder (even if it is pumped from tanks) you need to have the appropiate method of running the safety disharge pipes.

The Ariston range offer a 300 litre unvented tank with a reheat time of 18 minutes or so which is less than two metres tall.

thescruff · Moderator Joined: 03 May 2003 Posts: 4619 Location: Bath

What we need to do is assess the size of the property and maximum usage.

From your brief discription I can picture a manor type house of larger proportions than your 3bed semi.

For that type of property we would recommend a sectional tank of say 4/500 gallons with a purpose made pump booster set ( see twin CB400 pump set ) at amospumps.com.

A control panel with low level sensing device and a mains water bye-pass in the event of power failure.

Again the actual size would depend on demand.

Consider two smaller unvented cylinders against one big one, as they can be used for seperate areas such as the kitchen/utility and bathrooms, therefore reducing running costs.

To answer you question the pump would supply all the domestic water.

The section tanks is for ease of positioning a large storage.

To test the mains time how long it takes to fill a 5ltr bucket from a mains tap.

scruff. Cool