Shower installation help

[Piperdave22]

i have a client looking to have a pumped shower of some sort, open to options that will work ,
basically they have 25 gallons cold water storage cistern and 114litres 900 x 450 hot water water cylinder .
its an older property with a weird lay out which would mean the shower head is pretty much level with the bottom of the cws what would you suggest in this situation?

 

[steadyon]

1. The CWSC is too small for a pumped shower. 25 gallons is only about 115 litres, and that is nominal capacity. Actual could be a good bit lower.
2. If you can increase the storage, perhaps by installing an additional 25 gallon tank, properly linked to the existing one (water in one, out the other) you should be able to use a negative head pump.
3. Don't forget you will need a separate:
3a. Cold feed from the tank(s) to the pump, with the feed being slightly lower than the feed to the hot water cylinder.
3b. Hot feed from the cylinder, probably via a special flange to keep it air free. Look at the Stuart Turner and Salamander installation guides to see what is needed.
4. Pump should be at level of base of hot water cylinder for preference. Not under bath.

 

[Piperdave22]

1. The CWSC is too small for a pumped shower. 25 gallons is only about 115 litres, and that is nominal capacity. Actual could be a good bit lower.
2. If you can increase the storage, perhaps by installing an additional 25 gallon tank, properly linked to the existing one (water in one, out the other) you should be able to use a negative head pump.
3. Don't forget you will need a separate:
3a. Cold feed from the tank(s) to the pump, with the feed being slightly lower than the feed to the hot water cylinder.
3b. Hot feed from the cylinder, probably via a special flange to keep it air free. Look at the Stuart Turner and Salamander installation guides to see what is needed.
4. Pump should be at level of base of hot water cylinder for preference. Not under bath.

Thanks for the reply @steadyon would the hot cylinder storage be ok as the 115 litres isn't enough for the cold and there is only 114 litres for the hot ?

 

[Ric2013]

Thanks for the reply @steadyon would the hot cylinder storage be ok as the 115 litres isn't enough for the cold and there is only 114 litres for the hot ?

By CWSC, I suspect he means to say Combined Cylinder Feed and Cold Water Storage Cistern. You can, of course, have one cistern for the cold and one for the cylinder if you prefer.

It's not so big a deal if the cylinder runs cold as if the cistern runs empty, or near empty, and the pump drags in air.

 

[EvilDrPorkChop]

Upgrade the cold storage, Aqualisa Visage/Quartz pumped box.

They're always the easiest solution IMO for a pumped shower.

 

[Ben-gee]

Trouble with two separate tanks is you could run out of cold - but not hot and then you get scalded. So best to have linked tanks as per Steadyon.

 

[Piperdave22]

thanks for the replies , ill be upgrading the cold storage but will the hot need to be updated aswell or do you think that will be enough ?
the issue i have is that the shower head will be in a negative head position when on the hook being used and when they are spraying their body down it would be in a positive head position.
@EvilDrPorkChop the head would be above the cold water storage cistern level when in use . is the quartz compatible with that ?

 

[steadyon]

1. As far as I'm aware CWSC = Cold Water Storage Cistern and these normally feed the Hot Water Cylinder (HWC).
2. If the tanks weren't linked, you'd be back to exactly the situation you have now vis-a-vis a pumped shower.
3. The HWC would be better upgraded.
4. If you keep the existing HWC then:
4a. I think you'd get away with it provided the showers were reasonably short (10 minutes or thereabouts?).
4b. You would certainly need to wait between showers for the water to re-heat. Probably 20 to 40 minutes assuming a decent boiler. Two or even 3 hours on an immersion heater.
4c. It would be absolutely essential to ensure the cold supply to the HWC ran out before the cold supply to the shower. That way, if the cold tank starts to run dry, the hot at the shower is cut off before the cold. A cold shower is better than a scalding one.

 

[Ric2013]

1. As far as I'm aware CWSC = Cold Water Storage Cistern and these normally feed the Hot Water Cylinder (HWC).

Well, it stores cold water, so in that sense I'd agree, but if we call a cistern that feeds a cylinder a CWSC, one that serves cold taps a CWSC, and one that serves both purposes a CWSC it isn't clear to those on this forum that need to ask questions which we mean. My college textbooks (or perhaps it was in the WRAS blue book?) referred to a Combined Cylinder Feed and Cold Water Storage Cistern. Long winded, but at least there is no doubt what I mean when I use the term.

Of course we all call them a CWSC, but you can see that the OP might take this literally and now we've got him talking about 'upgrading the hot' and we don't know whether he means the cistern or the cylinder because we're all using terms loosely.

Also, I would note that (somewhat pedantically), the WRAS blue book insists on linking cisterns NOT one in and one out, but with separate float valves on each, balanced to kick in at the same time. Someone on this forum did once explain to me why, I think.

To reply to the OP, a negative head pump will work in positive head conditions. The basic difference is that a positive head one kicks in when it senses a gravity-induced flow, whereas the negative one senses that there is a drop in pressure due to a tap being opened.

Slightly critically, it does concern me though that you are asking these sorts of questions. While I'd rather you asked them than didn't ask them, it does strike me that you are rather out of your depth with a somewhat limited knowledge of showers, which worries me, given that this is not a DIY task but something you are taking on professionally. Are you sure you want this job? More constructively, if you're going to take on this kind of installation look up the "Mira's Guide to Pumped Showers". Once you've read and digested it, you'll be far more confident and knowledgeable.

 

[Piperdave22]

Thankyou for your replies @Ric2013 and @steadyon.
I am an experienced plumber , completing the work is no issue at all. but sizing up a shower pump has never been explained to me , I've worked for a company for many years and was pretty much just told where to put things and never really queried the reasons behind it.
I always like to work to a high standard and make sure I'm doing things 100 percent correctly hence trying to get my facts right before carrying out the work and advising the customer of the best option etc .

maybe it would be better if i wrote it like this ....
if you came to a job where they wanted a shower pump fitted to improve the shower pressure on a tank fed cylinder and cold water storage cistern , just using the one cold water storage cistern.
What would you suggest to them was the perfect cold water storage cistern and hot water cylinder size , i know it will depend on household but say you were basing it on worst case scenario on a 2bed,3bed and 4bed house ?

any response would be appreciated just to help me get my head round it all.

 

[steadyon]

1. CWSC 240 litres. Only bigger if really big house 6+ bedrooms.
2. HWC 180+ litres 2 or 3 bed, 210+ 4 bed.
3. Much bigger than 4 I'd be looking at unvented hot water 250 litres +

 

[Piperdave22]

1. CWSC 240 litres. Only bigger if really big house 6+ bedrooms.
2. HWC 180+ litres 2 or 3 bed, 210+ 4 bed.
3. Much bigger than 4 I'd be looking at unvented hot water 250 litres +

Thanks for the reply @steadyon