Best way to join 2 cold water tanks??

Daryll · 4 Aug 2011

Last year I replaced the old cold water tank in the loft with a bigger one, in anticipation of a bathroom re-fit and power shower which has now been done.

I've often wondered how much water the shower uses, (as I lay in bed listening to the tank refilling above me!), but the other day the water was off due to a burst water main, so after my daughter had showered and gone to work I went up in the loft and looked in the tank... the water level was about 2 inches above the outlet..!!

Some days 2 or even 3 of us take showers in quick sucession, so I'm now thinking I need to put a bigger tank in, or add another one....(I've heard bad things about Aqualisa showers if they run dry.)

The current tank is one of the 227 Ltr "coffin" tanks, about 60cm square by 1.5m ( the biggest I could fit through my loft hatch). If I bought another tank, which is the best way to connect the 2 tanks...?? a couple of 25mm pipes..? one 50mm pipe..??

(Both 22mm Hot and Cold shower feeds come from the tank)

Any ideas or suggestions welcome...

thanks,

Daryll.

xr4x4 · 4 Aug 2011

If 3 people have had showers and you haven't had a problem..... I dont see a problem.

gasafengineer · 4 Aug 2011

Considering the cistern is already installed i would couple the new cistern with some 42mm tube (or whatever would be cheapest) & fit ballvalve & overflow to new cistern , dependant on water main pressure you could just fit an additional ballvalve to existing cistern................might be lucky & find ballvalve full of ****e.

gasafengineer · 4 Aug 2011

Just re-read your post , seems the water main was off when the outlets were being used , what do you expect?

seco services · 4 Aug 2011

As said 227 ltr is useally quite Sufficient.

Daryll · 4 Aug 2011

Thanks Gents,

Yes, 3 of us have had showers, but I make sure the later people know to take a quick one..!

Luckily, the water went off on a saturday, so only my daughter needed a shower before work... if it had been a weekday there would have been a clear space around me in the office..!

Gassafengineer... yes, the mains was off, but if 1 person showering almost empties the tank, I've a feeeling its only luck we haven't run it dry before now...we have pretty low mains pressure, only just about 1 bar, so it takes a while to refill the tank... the shower almost certainly uses water faster than the mains refills it.

xr4x4 · 4 Aug 2011

Daryll said:
the shower almost certainly uses water faster than the mains refills it.

You sure about that?

Why don't you go up and watch the tank while someone is showering, I'd bet it's not as bad as you think.

Daryll · 4 Aug 2011

I will XR....I'm basing my assumption on the fact that we used to have a mains fed (15mm) electric shower, which was replaced with the Aqualisa Digital pumped shower.

The Aqualisa definatly puts out more water than the old one used to...!!

According to Aqualisa its putting out 13Ltr/minute, I've no idea what the flow rate is from the 15mm, 1 bar mains once it gets up into the loft, (maybe someone here can say??), but I'm sure its not 13Ltr a min....

Agile · 5 Aug 2011

Your 225 li tank will run a 13 li/min shower for 17 minutes without any refilling.

As a start you need to restrict shower usage to 7-8 minutes which is quite adequate for washing.

You need to make some measurements but the ball valve is quite restrictive. Adding a second one will get a higher refill rate or upsizing to a 3/4" or a 1" would give significant improvements in refill rates.

Tony

Agile · 5 Aug 2011

I am not convinced that a second tank is really necessary!

Tony

digdilem · 5 Aug 2011

Mostly with the others, but if you do decide to do it. there are two ways.

First is to join the two tanks with short lengths of pipe and tank connectors, as wide as you can cheaply get fittings for. The downside of this is that a leak in one will drain both and that the fittings sometimes leak.

The better way, if you can physically do it, is to fit the new tank entirely independantly and join its outlet pipe to the water take-off pipe alongside the existing, so you don't need to poke holes in any tanks.

An alternative is to make your existing tank fill quicker. Fitting /two/ ball valves increases input quite a lot, given that most ball valves are very restrictive and don't allow anywhere near full flow. I've done this with mine and not had a problem, although we only have one shower at a time, albiet a long one.

When they do run low, the pump noise changes quite dramatically. Making people aware that they turn off the shower if it stops producing water might be enough, as well as a pullcord isolator for the pump so power can be cut quickly. (I have this also because it fills my bath, and sometimes I only want a trickle so I just turn off the pump and get it coming through at normal pressures)

Daryll · 5 Aug 2011

Ok, thanks Gents for all your replies.

Maybe I was worrying too much... i'll have a look in the tank when someone is in the shower and see how low the level gets.

The suggestion of another ballvalve, or a bigger one, is probably the easiest thing to try before putting in another tank, if i am still concerned.

Thanks again..

Daryll.

algas · 5 Aug 2011

As Argyle said just up-rate your ballvalve to a 3/4" one this should give you plenty of mains water to fill the tank.

monoxide62 · 5 Aug 2011

................or simply change the high pressure orifice for a low pressure , shouldn't be a problem considering mains pressure quoted.

Boilerman2 · 5 Aug 2011

Increasing the amount of stored water in your attic will significantly increase the risk of Legionella, stale stored water and Showers are the biggest risk in contracting Legionaires disease!!!

I spend a lot of my time in Schools and similar buildings un-linking and de-commissioning oversized storage tanks to minimise the risks with regard water hygiene!!

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Best way to join 2 cold water tanks??

gasafengineer

gasafengineer

monoxide62

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